Wet response intelligent material based on waste textiles and preparation method and application thereof

Abstract

The invention belongs to the technical field of intelligent recycling of waste textiles, and particularly relates to a wet response intelligent material based on waste textiles and a preparation method and application of the wet response intelligent material. The method comprises the following steps: decoloring and cutting the waste cotton fabric into pieces, and carrying out phosphoric acid dissolution, dialysis and dispersion treatment to obtain a regenerated cellulose dispersion liquid; freeze-drying the regenerated cellulose dispersion liquid to form regenerated cellulose foam with a porous structure; the method comprises the following steps: cutting waste polyurethane waterproof cloth into pieces, and adding a solvent for dissolving to obtain regenerated polyurethane; mixing and drying the regenerated cellulose foam and the regenerated polyurethane, so that the regenerated cellulose foam and the regenerated polyurethane form a three-dimensional network through a physical cross-linking effect, and obtaining the wet response intelligent material. The wet response intelligent material based on the waste textiles shows a remarkable driving effect under humidity change, the driving time is only 60 seconds, the maximum bending angle can reach 70 degrees, and good intelligent response capacity is shown.

Description

Technical Field

[0001] The present invention belongs to the technical field of intelligent recycling of waste textiles, and specifically relates to a wet-responsive intelligent material based on waste textiles, and a preparation method and application thereof. Background Art

[0002] As a material that can respond to changes in environmental humidity, moisture-responsive smart materials have shown broad application prospects in the fields of smart textiles, sensors, and biomedical materials. In the existing technology, the preparation process of moisture-responsive materials mostly relies on high-purity raw materials, which are usually costly and mainly rely on the synthesis of new materials. Summary of the invention

[0003] In order to solve the above technical problems, the present invention provides a wet-responsive smart material based on waste textiles and a preparation method and application thereof. The present invention develops and designs smart materials based on the recycled products of waste textiles, utilizes cellulose and polyurethane polymer materials in waste textiles, prepares smart materials with good humidity response performance, and applies them to the field of wet-responsive smart fabrics, thereby realizing the recycling and reuse of waste textiles.

[0004] The present invention uses waste cotton fabric and waste polyurethane waterproof cloth as raw materials, and converts waste cotton fabric into regenerated cellulose foam through optimized decolorization and regeneration processes; converts waste polyurethane waterproof cloth into regenerated polyurethane through solvent dissolution treatment; uses regenerated polyurethane as a polymer matrix, uses regenerated cellulose foam as a filler, introduces regenerated cellulose foam into regenerated polyurethane, and forms a regenerated polyurethane-regenerated cellulose composite film with a porous structure and high hygroscopicity through physical crosslinking, as a wet-responsive smart material. When the humidity increases, the regenerated cellulose in the wet-responsive smart material absorbs moisture and expands, and the regenerated polyurethane in the wet-responsive smart material provides elastic support as a matrix, so that the overall structure of the wet-responsive smart material undergoes controllable deformation, realizes the humidity response function, and gives it shape memory and controllable deformation characteristics. The wet-responsive smart material is applied to 3D printing to achieve precise molding and structural design of the wet-responsive smart material, and to manufacture a wet-responsive material with a specific structure, such as a "valve", "flower" and "star-shaped flower" with a complex structure, to meet different application requirements.

[0005] The first object of the present invention is to provide a method for preparing a wet responsive smart material, comprising the following steps:

[0006] Step 1, preparing regenerated cellulose foam: using waste cotton fabric as raw material, decolorizing and shredding the waste cotton fabric, and then dissolving, dialyzing and dispersing the waste cotton fabric with phosphoric acid to convert the waste cotton fabric into regenerated cellulose to obtain a regenerated cellulose dispersion; freeze-drying the regenerated cellulose dispersion to form a regenerated cellulose foam with a porous structure.

[0007] It should be noted that the main component of waste cotton fabric is cellulose, which has excellent hygroscopicity and renewable utilization value. When using the cellulose in waste cotton fabric, it needs to be decolorized to remove the dyes and impurities in the waste cotton fabric and restore its original color. After decolorization, it can be used to prepare high-purity regenerated cellulose. The decolorization treatment of the present invention includes a reduction stage and an oxidation stage. The specific treatment process of the reduction stage is: soaking the waste cotton fabric in a mixed solution with a concentration of 10g / L to 30g / L, wherein the mixed solution is a mixture of a NaOH solution and a Na2O4S2 solution in a volume ratio of 1:1, and performing a reduction treatment for 1min to 3min; and treating the reduced cotton fabric with high-temperature steam at 80°C to 100°C, then washing with deionized water, and drying at 55°C to 65°C for 2h to obtain a dried cotton fabric; the specific treatment process of the oxidation stage is: soaking the dried cotton fabric in a H2O2 solution with a concentration of 10g / L to 15g / L, and adjusting the pH value of the H2O2 solution to 10 to 11, soaking for 4min to 6min, then washing and drying, to obtain the decolorized waste cotton fabric. After the decolorization treatment, it is ensured that the cellulose obtained in the subsequent steps has high purity and does not contain pigment impurities.

[0008] In addition, in order to make the decolorized waste cotton fabric dissolve faster, before using phosphoric acid solution to dissolve the waste cotton fabric; the present invention cuts the decolorized waste cotton fabric into pieces, and then adds phosphoric acid solution to the cut waste cotton fabric; under the action of phosphoric acid, the cellulose in the cotton fabric undergoes a hydrolysis reaction to form dissolved cellulose, i.e., cellulose phosphate, to obtain a phosphoric acid / cellulose solution; the phosphoric acid / cellulose solution is poured into deionized water and stirred sufficiently to regenerate the cellulose to obtain a regenerated cellulose suspension. Preferably, the mass fraction of the phosphoric acid solution is 80wt% to 90wt%; the temperature for dissolving the phosphoric acid is 45℃ to 55℃, and the dissolution time is 1h to 2h.

[0009] It should also be noted that the present invention disperses the regenerated cellulose suspension in a dispersant, and breaks the aggregation of cellulose molecules in the regenerated cellulose suspension through room temperature ultrasonic treatment, so that the cellulose molecules are evenly dispersed in the dispersant to obtain a regenerated cellulose dispersion. Preferably, the ultrasonic treatment time is 1h to 2h, and the ultrasonic treatment frequency is 20kHz to 40kHz to improve the dispersion effect of cellulose in the regenerated cellulose dispersion. At the same time, through a freeze-drying process, freeze-drying is carried out at -50℃ to -60℃ and 10Pa for 48h, so that the solvent in the regenerated cellulose dispersion is rapidly sublimated to form a regenerated cellulose foam with a porous structure, thereby increasing the specific surface area of ​​the regenerated cellulose and improving its humidity response performance. Preferably, the dispersant is a mixed solution of tert-butanol and water, and the volume ratio of tert-butanol to water is 1 to 99:1.

[0010] Step 2, preparing recycled polyurethane: using waste polyurethane tarpaulin as raw material, cutting the waste polyurethane tarpaulin into pieces and adding a solvent to dissolve the pieces, so as to convert the waste polyurethane tarpaulin into recycled polyurethane.

[0011] Polyurethane materials have excellent elasticity, durability and waterproof properties. By dissolving waste polyurethane tarpaulins, the polyurethane components can be recycled and reused. In order to completely dissolve the waste polyurethane tarpaulins, it is necessary to cut them into pieces before using solvent to dissolve them, and add solvent to the cut waste polyurethane tarpaulins to dissolve them. Since N,N-dimethylformamide is a polar solvent, it can effectively destroy the hydrogen bonds and hydrophobic effects between polyurethane molecules in polyurethane tarpaulins, so that the polyurethane molecules are evenly dispersed in the solution to form a transparent and uniform regenerated polyurethane solution, which is convenient for mixing with regenerated cellulose. Preferably, the solvent is N,N-dimethylformamide; preferably, the amount ratio of the waste polyurethane tarpaulin to the solvent is 1.5g~2.5g:50mL.

[0012] Step 3, preparing a regenerated polyurethane-regenerated cellulose composite membrane: using regenerated polyurethane as a polymer matrix and regenerated cellulose foam as a filler, mixing and drying the regenerated cellulose foam and regenerated polyurethane so that the regenerated cellulose foam and the regenerated polyurethane form a three-dimensional network through physical cross-linking to obtain a regenerated polyurethane-regenerated cellulose composite membrane, and using the regenerated polyurethane-regenerated cellulose composite membrane as a wet-responsive smart material.

[0013] It should be noted that the present invention mixes regenerated cellulose foam with regenerated polyurethane. During the mixing process, the cellulose in the regenerated cellulose foam and the polyurethane matrix in the regenerated polyurethane form a composite structure through physical interactions of hydrogen bonds and van der Waals forces. The solvent of the composite structure is evaporated by drying to form a stable three-dimensional network structure to obtain a regenerated polyurethane-regenerated cellulose composite film. The mass of the regenerated cellulose foam accounts for 20% to 40% of the mass of the regenerated polyurethane-regenerated cellulose composite film.

[0014] Since regenerated cellulose has excellent hygroscopicity, there are a large number of hydroxyl groups in the cellulose molecules, which can form hydrogen bonds with water molecules. When the ambient humidity increases, water molecules are adsorbed by the regenerated cellulose, causing the cellulose network structure to expand; while the regenerated polyurethane has good elasticity and recoverability, and can absorb external forces to a large extent and restore its original state; when the ambient humidity changes, the regenerated cellulose absorbs moisture and expands, while the regenerated polyurethane provides support and recovery in the structure. The porous structure in the regenerated polyurethane-regenerated cellulose composite membrane facilitates the rapid transfer of water molecules in the air, allowing the entire material to respond quickly when the humidity changes.

[0015] In addition, in order to make the regenerated cellulose foam and the regenerated polyurethane mix evenly, the present invention mixes them by ultrasonic treatment. Preferably, the mixing time of the regenerated cellulose foam and the regenerated polyurethane is 4h to 6h. At the same time, in order to facilitate the molding of the obtained regenerated polyurethane-regenerated cellulose composite film, the present invention mixes the regenerated cellulose foam and the regenerated polyurethane to obtain a mixed solution; the mixed solution is placed in a polytetrafluoroethylene mold, and dried at 55°C to 65°C for 10h to 14h to obtain a regenerated polyurethane-regenerated cellulose composite film. Preferably, the thickness of the regenerated polyurethane-regenerated cellulose composite film is 0.5mm to 2mm to meet the needs of the regenerated polyurethane-regenerated cellulose composite film in different application scenarios.

[0016] The present invention combines additive manufacturing technology with 3D printing technology to print wet-responsive smart materials according to a predetermined design. 3D printing technology can accurately control the arrangement and structure of materials to achieve complex shapes and specific functional designs. The present invention ensures the uniformity and smoothness of the printed structure and improves the overall performance of the material by optimizing printing parameters such as printing speed, temperature, filling angle and layer thickness. It can also achieve diversified intelligent structure programming, and can produce wet-responsive materials with complex structures such as "valves", "flowers" and "star-shaped flowers" with specific functions, which have good humidity-driven effects and are adaptable to different application requirements.

[0017] It should be noted that before using a 3D printer for printing, the present invention needs to cut the regenerated polyurethane-regenerated cellulose composite film into pieces and extrude it using a single screw extruder. By setting the extrusion temperature to 135°C to 145°C and the extrusion rate to 850rpm to 950rpm, a printed filament is obtained. Then a 3D printer is used for printing to produce a wet-responsive smart material with a specific structure. By using 3D printing technology to precisely shape the printed filaments and designing different geometric structures and pore distributions, the humidity response performance of the wet-responsive smart material can be enhanced.

[0018] The second object of the present invention is to provide a wet-responsive smart material prepared by the above preparation method.

[0019] The third object of the present invention is to provide application of the above-mentioned moisture-responsive smart material in the field of moisture-responsive smart fabrics.

[0020] Compared with the prior art, the present invention has the following beneficial effects:

[0021] The present invention utilizes waste material recycling technology, uses waste cotton fabrics and waste polyurethane waterproof cloth as raw materials, and converts waste cotton fabrics and waste polyurethane waterproof cloth into regenerated cellulose foam and regenerated polyurethane through optimized decolorization and dissolution regeneration processes, which not only achieves the resource utilization rate of waste textiles, but also improves the environmental friendliness and sustainability of the materials. In addition, the present invention adopts green chemical treatment and green preparation methods, avoids the use of toxic and harmful substances, reduces environmental pollution, and increases the safety and environmental protection of the process.

[0022] The present invention compounds regenerated cellulose foam with regenerated polyurethane. Since the regenerated cellulose foam has excellent hygroscopicity, when the ambient humidity changes, a large number of hydroxyl groups in the cellulose molecules of the regenerated cellulose foam can form hydrogen bonds with water molecules. Polyurethane has good elasticity and recoverability, and can absorb external forces to a large extent and return to its original state. When the ambient humidity increases, water molecules are adsorbed by the regenerated cellulose foam, causing the network structure of the regenerated cellulose foam to expand; and the polyurethane provides support and recovery in the structure. The porous structure in the regenerated polyurethane-regenerated cellulose composite film facilitates the rapid transfer of water molecules in the air, allowing the entire material to respond quickly when the humidity changes. The waste textile-based moisture-responsive smart material prepared by the present invention exhibits a significant driving effect under humidity changes, with a driving time of only 60 seconds and a maximum bending angle of up to 70°, showing good intelligent response capabilities.

[0023] The present invention combines additive manufacturing technology and optimizes printing parameters such as printing speed, temperature, filling angle and layer thickness to ensure the uniformity and smoothness of the printed structure and improve the overall performance of the material. It can also realize diversified intelligent structure programming, such as "valve", "flower" and "star-shaped flower" with complex structure of wet response materials, adapt to different application needs, and have good humidity driving effect. The 4D printed smart fabric based on the "valve" structure design can respond to moisture stimulation and show the effect of "close-open-close". It is suitable for the field of wet response smart fabrics and has good market prospects.

[0024] The smart material of the present invention is not only suitable for humidity management, but can also be extended to the design of other smart drivers, sensors and smart devices, and has broad application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 The figures are effect diagrams of the waste cotton fabric before and after bleaching according to Example 1 of the present invention; wherein (a) is after bleaching, and (b) is before bleaching.

[0026] Figure 2 It is a schematic diagram of the structure of the PU-RC "valve" prepared in Example 2 of the present invention before and after moisture actuation; wherein (a) is before moisture actuation, and (b) is after moisture actuation.

[0027] Figure 3 The wet response driving effect diagram of the PU-RC "valve" prepared in Application Example 2 of the present invention before and after moisture driving; wherein (a) is before moisture driving, and (b) is after moisture driving.

[0028] Figure 4 This is a schematic structural diagram of the PU-RC "star-shaped flower film" prepared in Application Example 3 of the present invention.

[0029] Figure 5 The wet response driving effect diagram of the PU-RC "star-shaped flower film" prepared in Application Example 3 of the present invention before and after moisture driving; wherein, (a) is before moisture driving, and (b) is after moisture driving.

[0030] Description of reference numerals:

[0031] 1- Passive layer; 2- Active layer. DETAILED DESCRIPTION

[0032] In order to enable those skilled in the art to better understand and implement the technical solution of the present invention, the present invention is further described below in conjunction with specific embodiments and drawings.

[0033] In the description of the present invention, unless otherwise specified, all reagents used are commercially available and all methods used are conventional techniques in the art.

[0034] The English name of recycled polyurethane is Reclaimed Polyurethane, abbreviated as PU in English; the English name of regenerated cellulose is Regenerated Cellulose, abbreviated as RC in English.

[0035] This embodiment provides a method for preparing a moisture-responsive smart material based on waste textiles.

[0036] Step 1: Preparation of regenerated cellulose:

[0037] 1.1) Soaking the waste cotton fabric in a mixed solution of NaOH and Na2O4S2 with a concentration of 20 g / L, wherein the volume ratio of the NaOH solution to the Na2O4S2 solution is 1:1, and performing a reduction treatment for 2 min; treating the cotton fabric after the reduction treatment with steam at a high temperature of 80°C, then washing it with deionized water for 4 times, and drying it at 60°C for 2 h to obtain a dry waste cotton fabric.

[0038] 1.2) Soaking the dried cotton fabric in a H2O2 solution with a concentration of 10 g / L, adjusting the pH to 10.5, soaking for 5 minutes, washing, and drying at 60°C for 2 hours to obtain decolorized waste cotton fabric.

[0039] 1.3) Cut the decolorized waste cotton fabric into pieces and dissolve it in 85% phosphoric acid solution at a temperature of 50° C. for 1 h to obtain a phosphoric acid / cellulose solution.

[0040] 1.4) Slowly pour the phosphoric acid / cellulose solution into 500 mL of deionized water and stir thoroughly to regenerate the cellulose to form a regenerated cellulose mixed solution.

[0041] 1.5) The regenerated cellulose suspension is placed in a dialysis bag and dialyzed in deionized water, with the dialysis water being replaced regularly until the pH value of the solution is close to neutral, thereby obtaining a regenerated cellulose suspension.

[0042] 1.6) Using tert-butyl alcohol and water in a volume ratio of 75:25 as a dispersant, the regenerated cellulose suspension is dispersed in the dispersant, and subjected to ultrasonic treatment for 1 hour to obtain a regenerated cellulose dispersion.

[0043] 1.7) freeze-drying the regenerated cellulose dispersion at -55°C and 10 Pa for 48 hours to obtain regenerated cellulose foam, i.e., regenerated cellulose.

[0044] Step 2: Preparation of recycled polyurethane:

[0045] 2 g of waste polyurethane waterproof cloth was cut into pieces, and 50 mL of N,N-dimethylformamide was added, and stirred at room temperature for 3 hours to obtain a regenerated polyurethane solution, namely, regenerated polyurethane.

[0046] Step 3: Preparation of wet responsive smart materials:

[0047] 3.1) 30% by mass of regenerated cellulose and 70% by mass of regenerated polyurethane were mixed and ultrasonically treated for 5 hours to obtain a mixed solution.

[0048] 3.2) The mixed solution was poured into a polytetrafluoroethylene mold and dried at 60°C for 12 h to obtain a regenerated polyurethane-regenerated cellulose composite membrane as a wet-responsive smart material.

[0049] Example 2

[0050] This embodiment provides a method for preparing a moisture-responsive smart material based on waste textiles.

[0051] Step 1: Preparation of regenerated cellulose:

[0052] 1.1) Soaking the waste cotton fabric in a mixed solution of NaOH and Na2O4S2 with a concentration of 10 g / L, wherein the volume ratio of the NaOH solution to the Na2O4S2 solution is 1:1, and performing a reduction treatment for 1 min; treating the cotton fabric after the reduction treatment with steam at a high temperature of 80°C, then washing it with deionized water for 4 times, and drying it at 55°C for 2 h to obtain a dry waste cotton fabric.

[0053] 1.2) Soak the dried cotton fabric in a H2O2 solution with a concentration of 15 g / L, adjust the pH to 10.5, soak for 4 minutes, then wash, and dry at 55°C for 2 hours to obtain decolorized waste cotton fabric.

[0054] 1.3) Cut the decolorized waste cotton fabric into pieces and dissolve it in 85% phosphoric acid solution at a temperature of 45° C. for 1 h to obtain a phosphoric acid / cellulose solution.

[0055] 1.4) Slowly pour the phosphoric acid / cellulose solution into 500 mL of deionized water and stir thoroughly to regenerate the cellulose to form a regenerated cellulose mixed solution.

[0056] 1.5) The regenerated cellulose suspension is placed in a dialysis bag and dialyzed in deionized water, with the dialysis water being replaced regularly until the pH value of the solution is close to neutral, thereby obtaining a regenerated cellulose suspension.

[0057] 1.6) Using tert-butyl alcohol and water in a volume ratio of 50:50 as a dispersant, the regenerated cellulose suspension is dispersed in the dispersant, and subjected to ultrasonic treatment for 1 hour to obtain a regenerated cellulose dispersion.

[0058] 1.7) freeze-drying the regenerated cellulose dispersion at -50°C and 10 Pa for 48 hours to obtain regenerated cellulose foam, i.e., regenerated cellulose.

[0059] Step 2, preparing recycled polyurethane: cut 1.5 g of waste polyurethane waterproof cloth into pieces, add 50 mL of N,N-dimethylformamide, and stir at room temperature for 2 hours to obtain a recycled polyurethane solution, i.e., recycled polyurethane.

[0060] Step 3: Preparation of wet responsive smart materials:

[0061] 3.1) 20% by mass of regenerated cellulose and 80% by mass of regenerated polyurethane were mixed and ultrasonically treated for 4 hours to obtain a mixed solution.

[0062] 3.2) The mixed solution was poured into a polytetrafluoroethylene mold and dried at 55°C for 10 h to obtain a regenerated polyurethane-regenerated cellulose composite membrane as a wet-responsive smart material.

[0063] Example 3

[0064] This embodiment provides a method for preparing a moisture-responsive smart material based on waste textiles.

[0065] Step 1: Preparation of regenerated cellulose:

[0066] 1.1) Soaking the waste cotton fabric in a mixed solution of NaOH and Na2O4S2 with a concentration of 30 g / L, wherein the volume ratio of the NaOH solution to the Na2O4S2 solution is 1:1, and performing a reduction treatment for 3 min; steaming the reduced cotton fabric at a high temperature of 100°C, then washing it with deionized water for 4 times, and drying it at 65°C for 2 h to obtain a dry waste cotton fabric.

[0067] 1.2) Soaking the dried cotton fabric in a H2O2 solution with a concentration of 20 g / L, adjusting the pH to 10.5, soaking for 6 minutes, then washing, and drying at 65°C for 2 hours to obtain decolorized waste cotton fabric.

[0068] 1.3) Cut the decolorized waste cotton fabric into pieces and dissolve it in 85% phosphoric acid solution at a temperature of 65° C. for 1 h to obtain a phosphoric acid / cellulose solution.

[0069] 1.4) Slowly pour the phosphoric acid / cellulose solution into 500 mL of deionized water and stir thoroughly to regenerate the cellulose to form a regenerated cellulose mixed solution.

[0070] 1.5) The regenerated cellulose suspension is placed in a dialysis bag and dialyzed in deionized water, with the dialysis water being replaced regularly until the pH value of the solution is close to neutral, thereby obtaining a regenerated cellulose suspension.

[0071] 1.6) Using tert-butyl alcohol and water in a volume ratio of 99:1 as a dispersant, the regenerated cellulose is dispersed in the dispersant, and subjected to ultrasonic treatment to obtain a regenerated cellulose dispersion.

[0072] 1.7) freeze-drying the regenerated cellulose dispersion at -60°C and 10 Pa for 48 h to obtain regenerated cellulose foam, i.e., regenerated cellulose.

[0073] Step 2, preparing recycled polyurethane: cut 2.5 g of waste polyurethane waterproof cloth into pieces, add 50 mL of N,N-dimethylformamide, and stir at room temperature for 4 hours to obtain a recycled polyurethane solution, namely, recycled polyurethane.

[0074] Step 3: Preparation of wet responsive smart materials:

[0075] 3.1) 40% by mass of regenerated cellulose and 60% by mass of regenerated polyurethane were mixed and ultrasonically treated for 6 hours to obtain a mixed solution.

[0076] 3.2) The mixed solution was poured into a polytetrafluoroethylene mold and dried at 65°C for 14 h to obtain a regenerated polyurethane-regenerated cellulose composite membrane as a wet-responsive smart material.

[0077] Comparative Example 1

[0078] This comparative example provides a method for preparing a recycled polyurethane film.

[0079] 2.5 g of waste polyurethane waterproof cloth was cut into pieces, and 50 mL of N,N-dimethylformamide was added, and stirred at room temperature for 4 hours to obtain a regenerated polyurethane solution.

[0080] The recycled polyurethane solution was poured into a polytetrafluoroethylene mold and dried at 65 °C for 14 h to obtain a recycled polyurethane film.

[0081] Application Example 1

[0082] This application embodiment provides a 3D printed wet-responsive smart material.

[0083] 1.1) The wet-responsive smart material prepared in Example 1 was cut into pieces and extruded using a single-screw extruder. The extrusion temperature was set to 140° C. and the extrusion rate was set to 900 rpm to obtain a printing filament.

[0084] 1.2) Using a 3D printer to print the printing filament to obtain a 3D printed wet responsive smart material.

[0085] Application Example 2

[0086] This application embodiment provides a 3D printed wet-responsive smart material.

[0087] 1.1) The wet-responsive smart material prepared in Example 2 was cut into pieces, and extruded using a single-screw extruder. The extrusion temperature was set to 135° C. and the extrusion rate was set to 850 rpm to obtain a first printing filament.

[0088] 1.2) The recycled polyurethane film prepared in Comparative Example 1 was cut into pieces and extruded using a single screw extruder. The extrusion temperature was set to 135° C. and the extrusion rate was set to 850 rpm to obtain a second printing filament.

[0089] 1.3) Designing the "valve" structure using computer-aided design software, converting the design model into 3D printing instructions using slicing software, and using a 3D printer to print the first printing filament and the second printing filament respectively to obtain the PU-RC "valve".

[0090] Application Example 3

[0091] This application embodiment provides a 3D printed wet-responsive smart material.

[0092] 1.1) The wet-responsive smart material prepared in Example 3 was cut into pieces and extruded using a single screw extruder. The extrusion temperature was set to 145° C. and the extrusion rate was set to 950 rpm to obtain a first printing filament.

[0093] 1.2) The recycled polyurethane film prepared in Comparative Example 1 was cut into pieces and extruded using a single screw extruder. The extrusion temperature was set to 145° C. and the extrusion rate was set to 950 rpm to obtain a second printing filament.

[0094] 1.3) Designing the "star-shaped flower" structure using computer-aided design software, converting the design model into 3D printing instructions using slicing software, and using a 3D printer to print the first printing filament and the second printing filament to obtain a PU-RC "star-shaped flower".

[0095] Figure 1The effect diagram of the waste cotton fabric of Example 1 after and before bleaching; wherein, (a) is after bleaching, and (b) is before bleaching. After being treated by the reduction-oxidation process, the bleaching effect of the waste cotton fabric is significant. The bleaching treatment mainly relies on two bleaching agents: Na2O4S2 and H2O2. In the reduction stage, the cotton fabric is immersed in a NaOH / Na2O4S2 solution and treated under high-temperature water vapor conditions. This process causes the cotton fiber to swell, thereby reducing the binding stability between the dye and the fiber. Subsequently, in the oxidation stage, H2O2 reacts with the easily oxidizable components in the dye, further weakening the binding force between the dye and the cotton fiber, causing the chromophore group of the dye to be oxidized, thereby achieving Figure 1 (a) to Figure 1 The decolorization effect of (b).

[0096] Figure 2 The schematic diagram of the structure of the PU-RC "valve" prepared in Example 2 before and after moisture actuation; (a) is before moisture actuation, and (b) is after moisture actuation. Figure 2 As can be seen in the figure, the PU-RC "valve" structure consists of an active layer 2 and a passive layer 1. The active layer 2 is a recycled polyurethane-regenerated cellulose layer with wet response characteristics; while the passive layer 1 is a recycled polyurethane layer used to suppress the humidity response of the active layer. Through this design, the wet responsiveness of the PU-RC "valve" can be programmed to achieve complex bending deformations, with a driving time of only 60 seconds and a maximum bending angle of up to 70°.

[0097] Figure 3 The wet response driving effect diagram of the PU-RC "valve" prepared in Example 2 before and after wet driving; (a) is before wet driving, and (b) is after wet driving. Figure 3 It can be seen that the recycled polyurethane-regenerated cellulose layer will absorb moisture and expand under moisture stimulation, causing the PU-RC "valve" to bend and deform, showing significant humidity responsiveness. The recycled polyurethane layer controls and regulates the response behavior of the recycled polyurethane-regenerated cellulose layer through its hydrophobic characteristics. The design of this double-layer structure enables the PU-RC "valve" to achieve an intelligent "open-closed" response under different humidity conditions. After removing moisture, the PU-RC "valve" can gradually return to its initial flat state. The rapid response and recovery ability of this process indicate that the structure has good adaptability and intelligent responsiveness under humidity changes, reflecting its reversible driving characteristics.

[0098] Figure 4 The schematic diagram of the structure of the PU-RC "star-shaped flower film" prepared in Example 3 is shown in FIG. Figure 4As shown in the figure, the structure of the PU-RC "star-shaped flower membrane" consists of multiple "petals", and the design inspiration comes from flowers in nature. Each "petal" is made of recycled polyurethane-regenerated cellulose material, as the active layer 2, which can deform under moisture stimulation; while the central "receptacle" is made of recycled polyurethane material, which plays the role of passive layer 1, limiting the overall humidity response. When moisture acts on the PU-RC "star-shaped flower membrane", the active layer 2 of the recycled polyurethane-regenerated cellulose layer absorbs moisture and expands, causing the "petals" to bend upward, simulating the process of flower opening. Due to the existence of the passive layer 1 of the recycled polyurethane layer, the "receptacle" remains relatively stable and does not participate in humidity drive, thereby realizing the selective drive of the "petals".

[0099] Figure 5 The PU-RC "star-shaped flower film" prepared in Example 3 is a wet response driving effect diagram before and after wet drive; wherein (a) is before wet drive, and (b) is after wet drive. Figure 5 As shown in the figure, under moisture stimulation, the bending degree of the "petals" in the PU-RC "star-shaped flower membrane" is closely related to the change in humidity. As the moisture increases, the "petals" gradually unfold, showing good moisture response performance. When the humidity reaches a certain threshold, the bending angle of the PU-RC "star-shaped flower membrane" can reach the maximum value within a few seconds; when the moisture is removed, the PU-RC "star-shaped flower membrane" can quickly return to its original state. This rapid response and recovery ability makes this material have a wide range of application potential in intelligent driving and adaptive systems.

[0100] It should be noted that when the present invention involves a numerical range, it should be understood that the two endpoints of each numerical range and any value between the two endpoints can be selected. Since the steps and methods used are the same as those in the embodiments, in order to avoid redundancy, the present invention describes a preferred embodiment. Although the preferred embodiments of the present invention have been described, once those skilled in the art know the basic creative concept, they can make other changes and modifications to these embodiments, and these changes and modifications all fall within the scope of the present invention.

[0101] Obviously, those skilled in the art can make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. If these modifications and variations of the present invention fall within the scope of the equivalent technology of the present invention, the present invention is also intended to include these modifications and variations.

Claims

1. A method for preparing a wet-responsive smart material based on waste textiles, characterized in that: The following steps are involved: Preparation of regenerated cellulose foam: using waste cotton fabric as raw material, decolorizing and shredding the waste cotton fabric, and then dissolving, dialyzing and dispersing the waste cotton fabric with phosphoric acid to convert the waste cotton fabric into regenerated cellulose to obtain a regenerated cellulose dispersion; freeze-drying the regenerated cellulose dispersion to form a regenerated cellulose foam with a porous structure; Preparation of recycled polyurethane: using waste polyurethane tarpaulin as raw material, cutting the waste polyurethane tarpaulin into pieces and adding a solvent to dissolve the waste polyurethane tarpaulin, so as to convert the waste polyurethane tarpaulin into recycled polyurethane; Preparation of regenerated polyurethane-regenerated cellulose composite membrane: using regenerated polyurethane as a polymer matrix and regenerated cellulose foam as a filler, the regenerated cellulose foam and regenerated polyurethane are mixed and dried to form a three-dimensional network through physical cross-linking of the regenerated cellulose foam and the regenerated polyurethane to obtain a regenerated polyurethane-regenerated cellulose composite membrane, and the regenerated polyurethane-regenerated cellulose composite membrane is used as a wet-responsive smart material.

2. The method for preparing a wet responsive smart material according to claim 1, characterized in that: The mass of the regenerated cellulose accounts for 20% to 40% of the mass of the polyurethane-regenerated cellulose composite film.

3. The method for preparing the wet responsive smart material according to claim 1, characterized in that: The dispersant is a mixed solution of tert-butanol and water, and the volume ratio of tert-butanol to water is 1-99:

1.

4. The method for preparing a wet responsive smart material according to claim 1, characterized in that: The usage ratio of the waste polyurethane waterproof cloth and the solvent is 1.5 g to 2.5 g: 50 mL.

5. The method for preparing a wet responsive smart material according to claim 1, characterized in that: The thickness of the regenerated polyurethane-regenerated cellulose composite film is 0.5 mm to 2 mm.

6. The method for preparing a wet responsive smart material according to claim 1, characterized in that: The mass fraction of the phosphoric acid solution is 80 wt% to 90 wt%.

7. The method for preparing a wet responsive smart material according to claim 1, characterized in that: The phosphoric acid is dissolved at a temperature of 45° C. to 55° C., and the dissolution time is 1 h to 2 h.

8. The method for preparing a wet responsive smart material according to claim 1, characterized in that: The regenerated cellulose and the regenerated polyurethane are mixed for 4 to 6 hours.

9. A method for preparing a moisture-responsive smart material according to any one of claims 1 to 8, wherein the method comprises preparing a moisture-responsive smart material.

10. Use of the moisture-responsive smart material according to claim 9 in moisture-responsive smart fabrics.

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