Recyclable polyethylene fiber reinforced silk protein composite material and preparation and recovery method thereof

Abstract

The invention discloses a recyclable polyethylene fiber reinforced silk protein composite material and a preparation and recovery method thereof. The preparation method comprises the following steps: preparing silk protein powder from waste silkworm cocoons or silk fabrics, dissolving the silk protein powder in an organic solvent to form a silk protein solution, infiltrating the polyethylene fibers, and naturally drying at normal temperature to obtain the composite material; the preparation method comprises the following steps: pressing polyethylene fibers into a plate, soaking the plate in a ternary solution, recycling under the condition of room temperature or water bath heating, taking out and separating the polyethylene fibers, and recycling to obtain the silk protein after dialysis treatment. The preparation process is simple, waste resources are fully utilized, and the production cost is effectively reduced; and the composite material can realize recycling of the polyethylene fiber and the silk protein through a mild recovery method, and has important significance for promoting sustainable development of the polyethylene fiber composite material.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of polyethylene fiber reinforced composites, and particularly relates to a recyclable polyethylene fiber reinforced silk fibroin composite material and a preparation and recycling method thereof. BACKGROUND

[0002] Polyethylene fiber reinforced composites exhibit important application value in the field of high-end equipment manufacturing due to their excellent lightweight high-strength, chemical corrosion resistance and impact resistance, but the recycling problem has become a key bottleneck restricting sustainable development. The recycling difficulties of the material mainly lie in that the stable cross-linked structure of the thermosetting resin matrix leads to difficulty in degradation; physical recycling can seriously damage the integrity and orientation structure of the fiber, and the recycled material can only be downgraded and applied in the field of low-value building materials; at the same time, the low melting point property (~ 150℃) of polyethylene fiber leads to thermal degradation in the pyrolysis process, affecting the mechanical properties of the recycled fiber.

[0003] In view of the above challenges, the current research focuses on developing recyclable green matrix material system, and exploring mild depolymerization process to realize clean and non-destructive separation of fiber and matrix. Through material system optimization and recycling technology innovation, it is expected to promote the development of polyethylene fiber reinforced composite materials in the whole life cycle towards high efficiency, high value and environmental friendliness. SUMMARY

[0004] In view of the problems existing in the field of polyethylene fiber reinforced composites, the present application proposes a recyclable polyethylene fiber reinforced silk fibroin composite material and a preparation and recycling method thereof, which uses silk fibroin extracted from waste cocoon or silk fabric to prepare polyethylene fiber composite material.

[0005] The present application successfully prepares a polyethylene fiber composite material with excellent mechanical properties by uniformly penetrating the polyethylene fiber with silk fibroin solution and forming by organic solvent volatilization drying. In addition, the present application also provides a mild recycling method, which can realize non-destructive and closed-loop recycling of polyethylene fiber and silk fibroin, effectively improving the recycling efficiency of the material. The present application not only integrates the recycling of waste resources, but also provides a new idea for the sustainable development of composite materials, and has broad application prospects.

[0006] The technical scheme of the present application comprises: One, a preparation method of a recyclable polyethylene fiber reinforced silk fibroin composite material, the method comprising the following steps: 1) preparing silk fibroin powder from waste cocoon or silk fabric; 2) dissolving the obtained silk fibroin powder in an organic solvent to prepare a silk fibroin solution with a certain concentration; 3) Pour the obtained silk protein solution into the mold containing polyethylene fibers uniformly, ensure that the solution completely immerses the polyethylene fibers, to form a uniform preliminary composite material, then place the preliminary composite material in a normal temperature environment for natural drying for 48 h to obtain a recyclable polyethylene fiber reinforced silk protein composite material.

[0007] The application develops a high-performance, recyclable polyethylene fiber composite material by utilizing waste silk resources. Compared with traditional thermosetting resins such as epoxy resin, phenolic resin and polyimide resin, the application not only realizes efficient integration of waste resources, but also realizes closed-loop recycling of polyethylene fibers and silk proteins under mild conditions because silk protein is a degradable natural polymer material. The method not only reduces the environmental burden of waste, but also provides a new solution for the sustainable development of polyethylene fiber composite materials.

[0008] The 1) is specifically: The waste cocoon or silk fabric is used as raw material, degumming treatment is carried out in a 0.5% mass fraction sodium carbonate solution, then washed with deionized water and oven dried; The dried silk protein is dissolved in a 9.3 M lithium bromide solution, and insoluble impurities are removed by filtration; Then, the silk protein solution is dialyzed in deionized water, and then the obtained silk protein aqueous solution is transferred to a refrigerator at -80 ℃ for freezing. After freezing, the solution is dried in a low-temperature vacuum environment by a freeze dryer, and finally silk protein powder is obtained.

[0009] In the 1), the degumming time of the waste cocoon or silk fabric ranges from 10 to 120 min; In the 1), the temperature for dissolving silk protein by lithium bromide ranges from 60 to 100 ℃, and the dissolving time is 1-5 h; the regenerated silk protein solution needs to be filtered. The waste silk contains many impurities after being dissolved by lithium bromide.

[0010] In the 1), the dialysis time is 3-5 days.

[0011] In the 2), the organic solvent is a fluorine-containing reagent, including hexafluoroisopropanol, trifluoroacetic acid and hexafluoroacetone, etc.; the fluorine-containing reagent is used to dissolve the silk protein powder, and the silk protein solution can maintain a stable spiral structure.

[0012] In the 2), the mass volume fraction of the silk protein solution is controlled between 5-30 g / mL. When the concentration of the silk solution is lower than 5 g / mL, the polyethylene fibers cannot be completely wrapped after the organic solvent volatilizes. When the concentration of the silk solution is higher than 20 g / mL, the viscosity is too high, which is not conducive to the uniform penetration of the solution into the polyethylene fibers.

[0013] In the 3), the type of polyethylene fiber includes short fiber, long fiber, fiber mat, fiber fabric with different weaving methods (including plain weave, twill weave, satin weave, and any combination thereof), and the like.

[0014] In the 3), the polyethylene fiber laminates are placed and then naturally dried at room temperature, and the drying time is not less than 12 h. The polyethylene fiber reinforced silk protein composite material cannot be too short, and when the drying time is less than 12 h, the solvent volatilization may not be complete, resulting in poor demolding effect.

[0015] II. A recycling method of a polyethylene fiber reinforced silk protein composite material, when the polyethylene fiber reinforced silk protein composite material is recycled, the method is as follows: S1, after the polyethylene fiber reinforced silk protein composite material is demolded, a marble plate is used to press to obtain a composite material plate; S2, the composite material plate is soaked in a specific ternary solution, and then placed at a selected appropriate temperature and time for recycling, the polyethylene fiber is separated from the liquid, and after cleaning and air drying, the polyethylene fiber can be reused; S3, the mixed solution after separating the polyethylene fiber in S2 is placed in deionized water and treated by dialysis to recycle the silk protein, so that the separation and recycling treatment is realized.

[0016] In the S1, the composite material needs to be pressed. The flatness of the composite material will affect the subsequent test of the material.

[0017] In the S2, the ternary solution is mainly composed of calcium chloride, ethanol mixed in water solvent, and the molar ratio of calcium chloride, ethanol and water is 1:2:8, and the water bath heating treatment is placed at a temperature range of 25-100 ℃, and the treatment time is 1 h-3 d. The higher the temperature, the faster the silk protein dissolving rate, and the water bath heating can not damage the overall morphology of the polyethylene fiber.

[0018] In the S3, the dialysis time is 3-5 d. When the dialysis time is less than 2 d, the obtained silk protein powder may contain residual calcium chloride and ethanol.

[0019] The method of the application uses polyethylene fiber as reinforcing material, uses silk protein extracted from waste cocoon or silk fabric as matrix material, uniformly penetrates the silk protein solution into the polyethylene fiber by solvent infiltration method, and forms a polyethylene fiber composite material by natural drying at room temperature. The preparation process is simple, fully utilizes waste resources, and effectively reduces the production cost. In addition, the composite material can realize the recycling of polyethylene fiber and silk protein through a mild recycling method, which has important significance for promoting the sustainable development of polyethylene fiber composite materials.

[0020] The beneficial effects of the present application are embodied in: (1) The present application uses polyethylene fibers as the reinforcing phase of the composite material, and uses silk fibroin obtained by dissolving waste cocoon as the matrix. The polyethylene fiber reinforced silk fibroin composite material has excellent mechanical properties.

[0021] (2) Compared with single polymer composites based on synthetic high molecules, the polyethylene fiber reinforced silk fibroin composite material prepared by the present application can realize the lossless closed-loop recycling of polyethylene fibers and silk fibroin.

[0022] (3) The preparation process of the present application is simple and easy to operate and has environmental friendliness, and is suitable for industrial scale production.

[0023] In summary, the matrix in the composite material in the present application is silk fibroin obtained by dissolving and regenerating waste cocoon. The obtained polyethylene fiber reinforced silk fibroin composite material has excellent mechanical properties. When the composite material reaches the service life, the polyethylene fibers and silk fibroin can be recycled by chemical dissolution method. The recycled material has excellent performance. BRIEF DESCRIPTION OF DRAWINGS

[0024] Figure 1 Scanning electron microscope images of the polyethylene fiber reinforced silk fibroin composite material prepared for Example 1 and Comparative Example 1; Figure 2 Stress-strain curve of the polyethylene fiber reinforced silk fibroin composite material prepared for Examples 1-4.

[0025] Figure 3 Process display diagram of the polyethylene fiber reinforced silk fibroin composite material prepared for Example 1, Comparative Examples 2-4.

[0026] Figure 4 SEM image of the recycled polyethylene fibers of the polyethylene fiber reinforced silk fibroin composite material prepared for Example 1, Comparative Examples 2-4.

[0027] Table 1 is the mechanical properties of the polyethylene fiber reinforced silk fibroin composite material of Examples 1-4. DETAILED DESCRIPTION

[0028] The present application will be further described below in conjunction with specific examples.

[0029] The embodiments of the present application are as follows: Example 1 (1) The waste cocoon is degummed in a 0.5% anhydrous sodium carbonate solution for 60 min, washed, dried and dissolved in a 9.3 M lithium bromide solution to obtain a silk protein aqueous solution, and the solution is dialyzed in deionized water for 3 days. The purified silk protein solution is frozen at -80 ℃, and low-temperature vacuum drying is performed by a freeze dryer to obtain a silk protein powder; (2) The silk protein powder obtained in step (1) is dissolved in hexafluoroisopropanol to prepare a 15 g / mL (mass fraction) silk protein solution; (3) The silk solution obtained in step (2) is poured into a polyethylene fiber fabric, and the solution is poured over the polyethylene fiber, and then the composite system is naturally dried at room temperature to obtain a polyethylene fiber reinforced silk protein composite material with a fiber content of 23%, and the scanning structure is shown in Figure 1 a.

[0030] The composite material is subjected to uniaxial tensile mechanical test, and the tensile strength of the composite material is 49.5±1.66 MPa, the elastic modulus is 0.4±0.01 GPa, and the elongation at break is 56.1±8.66%.

[0031] (4) The material obtained in step (3) is placed in a calcium chloride-ethanol-water (molar ratio 1:2:8) solution for recovery, and after soaking at room temperature for 6 h, the separated polyethylene fiber can be taken out from the solution, and the photo of the separated polyethylene fiber is shown in Figure 2 .

[0032] (5) The solution of the separated polyethylene fiber in step (4) is dialyzed for 3 days, and the silk protein can be recovered.

[0033] Example 2 (1) The silk fabric is degummed in a 0.5% anhydrous sodium carbonate solution for 60 min, washed, dried and dissolved in a 9.3 M lithium bromide solution to obtain a silk protein aqueous solution, and the solution is dialyzed in deionized water for 3 days. The purified silk protein solution is frozen at -80 ℃, and low-temperature vacuum drying is performed by a freeze dryer to obtain a silk protein powder; (2) The silk protein powder obtained in step (1) is dissolved in hexafluoroisopropanol to prepare a 15 g / mL (mass fraction) silk protein solution; (3) The silk solution obtained in step (2) is poured into a polyethylene fiber fabric, and the solution is poured over the polyethylene fiber, and then the composite system is naturally dried at room temperature to obtain a polyethylene fiber reinforced silk protein composite material with a fiber content of 23%, and the scanning structure is shown in

[0034] The composite material is subjected to uniaxial tensile mechanical test, and the tensile strength of the composite material is 52.3±2.34 MPa, the elastic modulus is 0.2±0.03 GPa, and the elongation at break is 100.3±1.81%.

[0035] (4) The material obtained in step (3) is placed in a calcium chloride-ethanol-water (molar ratio 1:2:8) solution for recovery. After soaking at room temperature for 6 h, the separated polyethylene fibers can be taken out of the solution.

[0036] (5) The solution of the separated polyethylene fibers in step (4) is dialyzed for 3 d, and the silk fibroin can be recovered.

[0037] Example 3 (1) The waste cocoon is degummed in a 0.5% by mass anhydrous sodium carbonate solution for 60 min, washed, dried, and dissolved in a 9.3 M lithium bromide solution to obtain a silk fibroin aqueous solution. The solution is dialyzed in deionized water for 3 d. The purified silk fibroin solution is frozen at -80 ℃, and low-temperature vacuum drying is performed by a freeze dryer to obtain a silk fibroin powder; (2) The silk fibroin powder obtained in step (1) is dissolved in hexafluoroisopropanol to prepare a 15 g / mL (mass / volume fraction) silk fibroin solution; (3) The silk solution obtained in step (2) is poured into a polyethylene fiber fabric, and the solution is made to cover the polyethylene fiber. Then, the composite system is naturally dried at room temperature to obtain a polyethylene fiber reinforced silk fibroin composite material with a fiber content of 40%.

[0038] The composite material is subjected to uniaxial tensile mechanical test, and the tensile strength of the composite material is 95.2±2.06 MPa, the elastic modulus is 0.3±0.02 GPa, and the elongation at break is 112.1±7.00%.

[0039] (5) The solution of the separated polyethylene fibers in step (4) is dialyzed for 3 d, and the silk fibroin can be recovered.

[0040] Example 4 (1) The silk fabric is degummed in a 0.5% by mass anhydrous sodium carbonate solution for 60 min, washed, dried, and dissolved in a 9.3 M lithium bromide solution to obtain a silk fibroin aqueous solution. The solution is dialyzed in deionized water for 3 d. The purified silk fibroin solution is frozen at -80 ℃, and low-temperature vacuum drying is performed by a freeze dryer to obtain a silk fibroin powder; (2) The silk fibroin powder obtained in step (1) is dissolved in hexafluoroisopropanol to prepare a silk fibroin solution with a mass fraction of 15 g / mL; (3) The silk solution obtained in step (2) is poured into a polyethylene fiber fabric, and the solution is made to cover the polyethylene fiber, and then the composite system is naturally dried at room temperature to obtain a polyethylene fiber reinforced silk fibroin composite material with a fiber content of 50%.

[0041] The composite material is subjected to uniaxial tensile mechanical test, and the tensile strength of the composite material is 114.8±9.66 MPa, the elastic modulus is 0.5±0.05 GPa, and the elongation at break is 110.2±1.50%.

[0042] (4) The material obtained in step (3) is placed in a calcium chloride-ethanol-water (molar ratio 1:2:8) solution for recovery, and after soaking at room temperature for 6 h, the separated polyethylene fiber can be taken out from the solution.

[0043] (5) The solution of the separated polyethylene fiber in step (4) is dialyzed for 3 days, and the silk fibroin can be recovered.

[0044] Examples 1-4 are taken as a group of experiments to perform tensile tests on polyethylene fiber reinforced silk fibroin composite materials with different fiber contents, as shown in Figure 2 and Table 1, and the recovery process of the polyethylene fiber reinforced silk fibroin composite material is shown in Figure 3 a.

[0045] Table 1 Mechanical properties of polyethylene fiber reinforced silk fibroin composite materials of Examples 1-4 To prove the necessity of the organic solvent (HFIP) preparation system and the superiority of the ternary solvent recovery system, a comparative example is specially set up for comparison and verification.

[0046] Comparative Example 1: The difference between this comparative example and Example 1 is that in step (2), hexafluoroisopropanol (HFIP) is not used as a solvent, but water is used as a solvent to prepare a silk fibroin solution (the electron microscope image of the material is shown in Figure 1 b). The specific modification is that the silk fibroin powder obtained in step (1) is dissolved in deionized water to prepare a silk fibroin aqueous solution with a mass fraction of 15 g / mL. In step (3), the aqueous solution is poured into a polyethylene fiber fabric, and the solution is made to cover the polyethylene fiber, and then the composite system is naturally dried at room temperature.

[0047] Comparative Example 2: The comparative example is based on the non-uniformly infiltrated polyethylene fiber reinforced silk fibroin composite material obtained in Comparative Example 1, and is recovered according to the scheme of the present application (the recovery process is shown in Figure 3 b). The specific difference is that the material obtained in Comparative Example 1 is placed in a calcium chloride-ethanol-water (molar ratio 1:2:8) solution for recovery, and soaked at room temperature for 3 h.

[0048] Comparative Example 3: The comparative example is based on the non-uniformly infiltrated polyethylene fiber reinforced silk fibroin composite material obtained in Comparative Example 1, and is recovered using a formic acid solution (the recovery process is shown in Figure 3 c). The specific difference is that the material obtained in Comparative Example 1 is placed in a formic acid solution, and soaked at room temperature for 3 h.

[0049] Comparative Example 4: The comparative example is based on the polyethylene fiber reinforced silk fibroin composite material obtained in Example 1, and is recovered using a formic acid solution (the recovery process is shown in Figure 3 d). The specific difference is that the material obtained in Example 1 is placed in a formic acid solution, and soaked at room temperature for 3 h, and then the polyethylene fibers are separated. After the solution of the separated polyethylene fibers is dialyzed for 3 d, the silk fibroin is recovered.

[0050] As shown in Figure 1 , Figures 3-4 Comparing the test results of the above Examples 1-4 and Comparative Examples 1-4 of the present application can see that: From the comparison of Comparative Example 1 and Examples 2-4, it can be seen that the selection of the solvent of the silk fibroin solution is a prerequisite for the preparation of a successful composite material. When a water system is used, the silk fibroin is not uniformly infiltrated, resulting in a large number of cracks in the polyethylene fiber reinforced silk fibroin composite material (Comparative Example 1, as shown in Figure 1 b), while the use of an organic solvent system such as hexafluoroisopropanol, trifluoroacetic acid, and hexafluoroacetone defined in the present application is the key to obtaining a polyethylene fiber reinforced silk fibroin composite material with uniform structure, good interfacial bonding, and excellent mechanical properties.

[0051] From the comparison of the recovery results of Comparative Example 2, Comparative Example 3, and Comparative Example 1, it can be seen that the ternary recovery system (CaCl2 / EtOH / H2O) of the present application has strong universality and mildness. Even for a non-uniformly infiltrated composite material, the components can be efficiently and non-destructively separated (Comparative Example 2, as shown in Figure 3 b, 4b). The formic acid recovery method not only has poor separation effect on such materials, but also causes damage to the fibers (Comparative Example 3, as shown in Figure 3 c, 4c).

[0052] From the direct comparison of the recovery results of Comparative Example 4 and Example 4, it can be seen that for high-performance composites, the ternary recovery system of the present application is far superior to the formic acid method in maintaining the intrinsic properties of the recovered materials (polyethylene fibers and silk fibroin). Formic acid can damage polyethylene fibers (such as Figure 3 d, 4d), while the method of the present application can achieve near-closed-loop high-value recycling.

[0053] In summary, the method of the present application uses waste silk and cocoon as initial raw materials, and the good interfacial bonding of silk fibroin matrix and polyethylene fibers in the composite material gives the material excellent mechanical properties. The present application creatively constructs a complete technical scheme from "preparation in organic solvent system" to "mild recovery in ternary system", which complements each other and solves the problems of difficult preparation and difficult recovery of silk fibroin-based composites, reduces resource waste, improves resource utilization, and is conducive to promoting the recycling of polyethylene fibers. As can be seen from the above examples, the method of the present application uses waste silk and cocoon as initial raw materials, and the good interfacial bonding of silk fibroin matrix and polyethylene fibers in the composite material gives the material excellent mechanical properties. And the closed-loop recovery of polyethylene fibers and silk fibroin can be carried out in a simple way, which reduces resource waste, improves resource utilization, and is conducive to promoting the recycling of polyethylene fibers.

[0054] The above specific embodiments are used to explain and illustrate the present application, rather than limit the present application, and any modifications and changes made to the present application within the spirit and protection scope of the claims fall within the protection scope of the present application.

[0055] The above is only the preferred embodiment of the present application, therefore, any equivalent changes or modifications made to the structure, features and principles described in the scope of the present application patent application are included in the scope of the present application patent application.

Claims

1. A method for preparing a recyclable polyethylene fiber-reinforced silk fibroin composite material, characterized by: The method comprises the following steps: 1) preparing silk fibroin powder from waste cocoon or silk fabric; 2) dissolving the obtained silk fibroin powder in an organic solvent to prepare a silk fibroin solution; 3) uniformly pouring the obtained silk fibroin solution into a mold containing polyethylene fibers to form a uniform preliminary composite material, and then placing the preliminary composite material in a normal temperature environment for natural drying to obtain a recyclable polyethylene fiber reinforced silk fibroin composite material.

2. The method for preparing the recyclable polyethylene fiber reinforced silk fibroin composite material according to claim 1, characterized in that: The 1) is specifically: The waste cocoon or silk fabric is used as raw material, degumming treatment is carried out in a sodium carbonate solution, then washed with deionized water, and dried in an oven; The dried silk fibroin is dissolved in a 9.3 M lithium bromide solution, and insoluble impurities are removed by filtration; Then, the silk fibroin solution is dialyzed in deionized water, and then the obtained silk fibroin aqueous solution is transferred to a refrigerator at -80℃ for freezing, and the solution is dried in a low-temperature vacuum environment by a freeze dryer after freezing, and finally the silk fibroin powder is obtained.

3. The preparation method of the recyclable polyethylene fiber reinforced silk fibroin composite material according to claim 1, characterized in that: In the 1), the degumming time of the waste cocoon or silk fabric ranges from 10 to 120 min; In the 1), the temperature for dissolving the silk fibroin in lithium bromide ranges from 60 to 100℃, and the dissolving time is 1-5 h; In the 1), the dialysis time is 3-5 d.

4. The method for preparing the polyethylene fiber reinforced silk fibroin composite material according to claim 1, characterized in that: In the 2), the organic solvent is selected from fluorine-containing reagents, including hexafluoroisopropanol, trifluoroacetic acid and hexafluoroacetone, etc.; the mass fraction of the silk fibroin solution is controlled between 5-30 g / mL.

5. The method for preparing the polyethylene fiber reinforced silk fibroin composite material according to claim 1, characterized in that: In the 3), the types of polyethylene fibers include short fibers, long fibers, fiber thin felt, fiber fabrics with different weaving methods, etc.

6. The method for preparing the polyethylene fiber reinforced silk fibroin composite material according to claim 1, characterized in that: In the 3), the polyethylene fiber laminates are placed and then naturally dried at room temperature, and the drying time is not less than 12 h.

7. A polyethylene fiber-reinforced silk fibroin composite material characterized by: The preparation method is prepared by any one of claims 1-6.

8. The recycling method of the polyethylene fiber-reinforced silk fibroin composite material according to claim 7, characterized in that: The method is as follows: S1, the polyethylene fiber reinforced silk fibroin composite material is pressed with a marble plate to obtain a composite material plate; S2, the composite material plate is soaked in a ternary solution, and then placed at a selected appropriate temperature and time for recycling, and the polyethylene fiber is separated from the liquid, and after cleaning and air drying, the polyethylene fiber can be reused; S3, the mixed solution after separating the polyethylene fiber in S2 is placed in deionized water for dialysis treatment, and then the silk fibroin is recovered.

9. The recycling method according to claim 8, characterized in that: In the S2, the ternary solution is mainly composed of calcium chloride, ethanol mixed in water solvent, and the molar ratio of calcium chloride, ethanol and water is 1:2:8, and the water bath heating treatment is placed at a temperature range of 25-100℃, and the treatment time is 1 h-3 d.

10. The recycling method according to claim 8, characterized in that: In the S3, the dialysis time is 3-5 d.

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