Hyperelastic 3D printing nano cellulose composite material and preparation method thereof

Abstract

The invention provides a superelastic 3D printing nanocellulose composite material and a preparation method thereof.The preparation method comprises the steps that nanocellulose is extracted, nanocellulose is extracted from natural fibers in a sulfuric acid hydrolysis mode, the nanocellulose, polyvinyl alcohol PVA and polyurethane PU are stirred and mixed, a precursor solution of the composite material is prepared, and the superelastic 3D printing nanocellulose composite material is obtained; parameters are set through a 3D printer, the composite material precursor solution is printed into the needed shape and structure layer by layer, after printing is completed, the formed composite material is subjected to heat treatment, the composite material subjected to heat treatment is subjected to performance testing, and preparation work is completed; the composite material extracted and prepared by the preparation method of the composite material has excellent elastic recovery capability, recovers to the original shape after large deformation and is suitable for application scenes needing repeated deformation, the biodegradability of the nanocellulose enables the composite material to have the characteristic of environmental friendliness, and the composite material can be applied to 3D printing through a 3D printing technology. And customizing the shape and the structure of the composite material as required.

Description

Technical Field

[0001] The present invention relates to the technical field of 3D printing materials, and in particular to a superelastic 3D printing nanocellulose composite material and a preparation method thereof. Background Art

[0002] 3D printing enables the customization of complex macro and micro structures. 3D printing can be used in the preparation of functional materials to leverage its structural customization advantages, helping to promote the development of functional materials and unlocking enormous application potential. Currently, due to limitations in molding technology, 3D printable polymers and composite materials are extremely limited. Cellulose is not only widely available, abundant in reserves, and environmentally friendly, but its excellent mechanical properties have also attracted widespread attention from researchers. The polymer's adjustable viscosity in solution and shear-thinning properties provide the necessary conditions for 3D printing processing.

[0003] In Chinese Patent No. 201810349204.4, the inorganic nanoparticle aqueous solution cannot be 3D printed due to its extremely low viscosity and concentration. Conventional 3D printing methods rely on high-temperature melting and other methods, which easily cause problems such as biomass carbonization. Therefore, the present invention proposes a super-elastic 3D printed nanocellulose composite material and its preparation method to solve the problems existing in the prior art. Summary of the Invention

[0004] In response to the shortcomings of the existing technology, the present invention proposes a super-elastic 3D printed nanocellulose composite material and a preparation method thereof. The composite material of the super-elastic 3D printed nanocellulose composite material and the preparation method thereof has excellent elastic recovery ability and returns to its original shape after undergoing large deformation. It is suitable for application scenarios that require repeated deformation. The biodegradability of nanocellulose makes the composite material environmentally friendly and reduces pollution to the environment. Through 3D printing technology, the shape and structure of the composite material can be customized as needed to meet the needs of specific applications. The composite material can be given special properties by adding different functional additives.

[0005] The technical solution of the present invention is achieved as follows: a superelastic 3D printed nanocellulose composite material and a preparation method thereof, comprising the following steps;

[0006] Step 1: Prepare natural fibers and perform nanocellulose extraction, extracting nanocellulose from natural fibers by sulfuric acid hydrolysis;

[0007] Step 2: After preparing polyvinyl alcohol and polyurethane, the extracted nanocellulose is stirred and mixed with the polyvinyl alcohol and polyurethane to prepare a precursor solution of the composite material;

[0008] Step 3: The prepared precursor solution is introduced into a 3D printer, and the composite material precursor solution is printed layer by layer into the desired shape and structure using the 3D printer with the parameters set;

[0009] Step 4: After printing is completed, the molded composite material is heat treated;

[0010] Step 5: Perform performance tests on the heat-treated molded composite material to complete the preparation work.

[0011] A further improvement is that in step 1, the nanocellulose is microcrystalline cellulose, and the microcrystalline cellulose is hydrolyzed with sulfuric acid to remove lignin and hemicellulose, leaving purified cellulose.

[0012] A further improvement is that in step 2, polyvinyl alcohol and polyurethane solutions are prepared, dissolved in water, and then the nanocellulose and the dissolved polyvinyl alcohol and polyurethane solutions are placed in a mixing device for stirring and mixing, and a plasticizer is added during the stirring process and slowly stirred to complete sufficient mixing.

[0013] Further improvements are: in step three, the required three-dimensional model is designed using computer-aided design software, the designed three-dimensional model is imported into slicing software, the model is cut into multiple thin layers, the printing path and filling pattern are generated, the 3D printer is started, and printing begins layer by layer. The print head moves according to the set path, and the composite material precursor solution is deposited on the printing platform to form a layer-by-layer structure to complete the printing work.

[0014] A further improvement is that in step 4, the material is cleaned before being heat-treated, the material is placed in a vacuum box, and the vacuum box is slowly heated to complete the heat treatment of the internal material.

[0015] Further improvements are: in step five, the performance test includes a tensile test, which is performed by placing the material on a testing machine, fixing both sides of the material with a clamp, setting the tensile speed, and the parameter between 5 mm / min and 50 mm / min. The material is tensile tested at the set speed, and the tensile data is saved and recorded at the same time, and the prepared material is used for strength testing.

[0016] A further improvement is that in step 1, the nanocellulose includes microcrystalline cellulose, TEMPO oxidized cellulose, hydroxymethyl cellulose and enzymatically hydrolyzed nanocellulose, preferably microcrystalline cellulose and oxidized cellulose.

[0017] A further improvement is that in step three, the printing speed is 2 to 6 mm / s, the material extrusion speed is 1 to 3 mL / h, and the nozzle diameter is 0.2 to 0.6 mm.

[0018] A further improvement is that in step 4, the material is placed in a 0.1-2 mol / L hygroscopic salt solution and soaked for 1 minute before the molding material is heat-treated.

[0019] Compared with the existing technology, the present invention has the following advantages: the composite material prepared by the composite material preparation method has excellent elastic recovery ability, and returns to its original shape after large deformation, which is suitable for application scenarios that require repeated deformation. The biodegradability of nanocellulose makes the composite material environmentally friendly and reduces pollution to the environment. The addition of polyvinyl alcohol and polyurethane solutions avoids biomass carbonization. Through 3D printing technology, the shape and structure of the composite material can be customized according to needs to meet the needs of specific applications. The composite material can be given special properties including conductivity, antibacterial and self-healing ability by adding different functional additives. The composite material combines the high strength and high modulus of nanocellulose with the flexibility and processability of polymers, and has good mechanical properties. The combination of nanocellulose and 3D printing technology has promoted the development of materials science and manufacturing technology. The composite material is suitable for biomedicine, packaging materials, sensors and structural materials and other fields. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0021] Figure 1 It is a flow chart of the steps of the present invention. DETAILED DESCRIPTION

[0022] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0023] In the document 201810349204.4, a first portion of solvent and a first nanocellulose are mixed to prepare a first nanocellulose dispersion; the diameter of the first nanocellulose is 1 to 50 nm, and the aspect ratio is 50:1 to 100:1. A second nanocellulose, a second portion of solvent and polyacrylonitrile are added to the first nanocellulose dispersion and mixed uniformly to obtain a spinning solution; the diameter of the second nanocellulose is 50 to 100 nm, and the aspect ratio is 10:1 to 50:1. The spinning solution is wet-spun to obtain nanocellulose-modified acrylic fibers. This application prepares nanocelluloses with different aspect ratios, firstly mixing the nanocelluloses with a large aspect ratio and then spinning them. The first nanocellulose is dispersed, the nanocellulose is overlapped into a web, and then the second nanocellulose is dispersed and adsorbed on the web, which can avoid the agglomeration of nanocellulose, improve the dispersibility, and improve the stability of nanocellulose in the spinning solution, and will not agglomerate or precipitate due to standing. However, the viscosity and concentration of the nanocellulose are not enough for 3D printing, and 3D printing technology cannot be used. In this application, the viscosity and concentration of the prepared fiber material are increased and then 3D printing is performed. The shape and structure of the composite material can be customized as needed to meet the needs of specific applications. The composite material can be given special properties by adding different functional additives.

[0024] See also Figure 1 , an embodiment of the present invention discloses a superelastic 3D printed nanocellulose composite material and a preparation method thereof, comprising the following steps;

[0025] Step 1: Prepare natural fibers and perform nanocellulose extraction, extracting nanocellulose from natural fibers by sulfuric acid hydrolysis;

[0026] Step 2: After preparing polyvinyl alcohol and polyurethane, the extracted nanocellulose is stirred and mixed with the polyvinyl alcohol and polyurethane to prepare a precursor solution of the composite material, wherein the concentration of the nanocellulose is 0.1wt%-5wt%, the concentration of the polyvinyl alcohol is 1wt%-15wt%, and the concentration of the polyurethane is 1wt%-10wt%;

[0027] Step 3: The prepared precursor solution is introduced into a 3D printer, and the composite material precursor solution is printed layer by layer into the desired shape and structure using the 3D printer with the parameters set;

[0028] Step 4: After printing is completed, the molded composite material is heat treated;

[0029] Step 5: Perform performance tests on the heat-treated molded composite material to complete the preparation work.

[0030] In step one, the nanocellulose is microcrystalline cellulose, which is hydrolyzed by sulfuric acid to remove lignin and hemicellulose, leaving purified cellulose. During the hydrolysis process, the cellulose is mixed with concentrated sulfuric acid and hydrolyzed at 0°C to 25°C. The sulfuric acid concentration is 64%-68%. The sulfuric acid causes the cellulose chain to break, thereby forming a nanoscale. The nanocellulose is then dispersed in water to form a stable suspension. At the same time, a stabilizer is added, which is a surfactant to prevent the nanocellulose from agglomerating.

[0031] In step 2, polyvinyl alcohol and polyurethane solutions are prepared and dissolved in water, and then the nanocellulose and the dissolved polyvinyl alcohol and polyurethane solutions are placed in a mixing device for stirring and mixing. During the stirring process, a plasticizer is added and slowly stirred, and finally, sufficient mixing is completed. After the mixing is completed, the bubbles in the solution are removed to obtain a precursor solution, and then the precursor solution is placed in a sealed container for storage for subsequent use.

[0032] In step three, use computer-aided design software to design the required three-dimensional model, import the designed three-dimensional model into the slicing software, cut the model into multiple thin layers, generate the printing path and filling pattern, set the printing parameters, including layer thickness, printing speed and nozzle temperature, the layer thickness is 200 microns, the printing speed is 50 mm / s, and the nozzle temperature is 200 degrees Celsius. After the parameters are set, the composite material precursor solution is loaded into the nozzle of the 3D printer, the 3D printer is started, and printing begins layer by layer. The print head moves according to the set path, depositing the composite material precursor solution on the printing platform to form a layer-by-layer structure to complete the printing work.

[0033] In step four, the material is cleaned before heat treatment, and then placed in a vacuum box, which is then slowly heated. The internal temperature of the vacuum box is 36°-200°, and the internal material is heat treated. During the heat treatment, the internal heat is controlled to avoid internal stress and deformation of the material due to excessive temperature gradients. The heating rate is slow to ensure that the material is heated evenly. The use of heat treatment promotes the rearrangement and crystallization of polymer chains, thereby improving the strength, modulus and toughness of the composite material.

[0034] In step five, the performance test includes a tensile test, which is performed by placing the material on a testing machine, fixing both sides of the material with a clamp, setting the tensile speed, and saving and recording the tensile data at the set speed. The prepared material is then subjected to a strength test, and a universal material testing machine is used for compression testing. Ensure that the pressure head of the testing machine is parallel to the surface of the material and can provide a uniform compression speed. Set a suitable compression speed between 0.5 and 5 mm / min, and compress the specimen at the set speed until the material reaches a predetermined strain or is damaged. Record the force during the compression process, from which the stress can be calculated. Extract key mechanical performance parameters from the stress, including compression strength, compression modulus, and yield point, to ensure stable control of material quality.

[0035] In step one, the nanocellulose includes microcrystalline cellulose, TEMPO oxidized cellulose, hydroxymethyl cellulose and enzymatically hydrolyzed nanocellulose, preferably microcrystalline cellulose and oxidized cellulose.

[0036] In step three, the printing speed is 2 to 6 mm / s, the material extrusion speed is 1 to 3 mL / h, and the nozzle diameter is 0.2 to 0.6 mm.

[0037] In step 4, the molding material is immersed in a 0.1-2 mol / L hygroscopic salt solution for 1 minute before heat treatment. The hygroscopic salt can absorb moisture in the air. The salt penetrates evenly into the material through soaking, giving the material hygroscopicity. The ions of the hygroscopic salt migrate inside the material, which can increase the ionic conductivity of the material.

[0038] This super-elastic 3D printed nanocellulose composite material and its preparation method extract nanocellulose from natural fibers, hydrolyze it with sulfuric acid, mix the nanocellulose with polyvinyl alcohol (PVA) and polyurethane (PU) to form a precursor solution of the composite material, add a plasticizer to improve the performance of the composite material, and use a 3D printer to print the composite material precursor solution layer by layer into the desired shape and structure. After printing, the composite material is heat treated to improve its mechanical properties and stability. The prepared composite material is subjected to mechanical property tests, tensile tests, and compression tests to evaluate its super-elastic properties, and biocompatibility tests are performed to ensure that the material is suitable for various fields such as biomedicine.

[0039] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for preparing a superelastic 3D printed nanocellulose composite material, characterized in that: The following steps are included: Step 1: Extracting nanocellulose from natural fibers by sulfuric acid hydrolysis; Step 2: Mixing the extracted nanocellulose with polyvinyl alcohol and polyurethane to prepare a precursor solution of the composite material; Step 3: The prepared precursor solution is introduced into a 3D printer, and the composite material precursor solution is printed layer by layer into the desired shape and structure using the 3D printer with the parameters set; Step 4: After printing is completed, the molded composite material is heat treated; Step 5: Perform performance tests on the heat-treated molded composite material to complete the preparation work.

2. The method for preparing a superelastic 3D printed nanocellulose composite material according to claim 1, characterized in that: In the step 1, the nanocellulose is microcrystalline cellulose, and the microcrystalline cellulose is hydrolyzed by sulfuric acid to remove lignin and hemicellulose, leaving purified cellulose.

3. The method for preparing a superelastic 3D printed nanocellulose composite material according to claim 1, characterized in that: In the second step, polyvinyl alcohol and polyurethane solutions are prepared and dissolved in water, and then the nanocellulose and the dissolved polyvinyl alcohol and polyurethane solutions are placed in a mixing device for stirring and mixing. During the stirring process, a plasticizer is added and stirred slowly, and finally, sufficient mixing is completed.

4. The method for preparing a superelastic 3D printed nanocellulose composite material according to claim 1, characterized in that: In step three, the precursor solution is introduced into the 3D printer, the required three-dimensional model is designed using computer-aided design software, the designed three-dimensional model is imported into the slicing software in the 3D printer, the model is cut into multiple thin layers, the printing path and filling pattern are generated, the 3D printer is started, and printing begins layer by layer. The print head moves according to the set path, depositing the composite material precursor solution on the printing platform to form a layer-by-layer structure to complete the printing work.

5. The method for preparing a superelastic 3D printed nanocellulose composite material according to claim 1, characterized in that: In the step 4, the material is cleaned before being heat-treated, and then placed in a vacuum box, which is then slowly heated to complete the heat treatment of the internal material.

6. The method for preparing a superelastic 3D printed nanocellulose composite material according to claim 1, characterized in that: In step five, the performance test includes a tensile test, which is performed by placing the material on a testing machine, fixing both sides of the material with a clamp, setting the tensile speed with a parameter between 5 mm / min and 50 mm / min, and performing a tensile test on the material at the set speed. At the same time, the tensile data is saved and recorded, and the prepared material is used for strength testing.

7. The method for preparing a superelastic 3D printed nanocellulose composite material according to claim 1, characterized in that: In the step 1, the nanocellulose includes microcrystalline cellulose, TEMPO oxidized cellulose, hydroxymethyl cellulose and enzymatically hydrolyzed nanocellulose.

8. The method for preparing a superelastic 3D printed nanocellulose composite material according to claim 1, characterized in that: In step three, the printing speed is 2 to 6 mm / s, the material extrusion speed is 1 to 3 mL / h, and the nozzle diameter is 0.2 to 0.6 mm.

9. The method for preparing a superelastic 3D printed nanocellulose composite material according to claim 1, characterized in that: In the fourth step, the molding material is immersed in a 0.1-2 mol / L hygroscopic salt solution for 1 minute before heat treatment.

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