A high-strength and anti-swelling polyvinyl alcohol hydrogel material and a 3D printing preparation method thereof
By using rheology enhancers and alkali-solvent displacement/salting-out processes, the problems of easy swelling and mechanical property degradation of traditional PVA hydrogels in aqueous environments have been solved, enabling the preparation of high-strength, swelling-resistant 3D-printed hydrogels with complex shapes, thus improving the printability and mechanical properties of the material.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- DALIAN POLYTECHNIC UNIVERSITY
- Filing Date
- 2026-04-27
- Publication Date
- 2026-06-23
AI Technical Summary
Traditional PVA hydrogels are prone to swelling and mechanical property degradation in aqueous environments, making it difficult to manufacture complex shapes. Existing 3D printing hydrogels cannot simultaneously achieve printability, mechanical properties, and swelling resistance.
High-strength, swelling-resistant polyvinyl alcohol hydrogels were prepared by 3D printing using rheology modifier-modified material formulation design and alkali-solvent replacement/salting-out synergistic process. This included the use of reinforcing agents such as cellulose nanofibers, and the formation of a dense microcrystalline network through alkali treatment and salting-out solvent replacement.
The prepared hydrogel maintains high strength and low swelling in an aqueous environment, enabling precise printing of complex shapes and improving the mechanical properties and structural stability of the material.
Smart Images
Figure CN122255641A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of polymer hydrogel materials technology, and relates to a high-strength and swelling-resistant polyvinyl alcohol hydrogel material and its 3D printing preparation method. Background Technology
[0002] Traditional PVA hydrogels suffer from three major drawbacks: poor swelling stability (easily expanding in volume and degrading mechanical properties in aqueous environments, severely limiting their application in underwater or humid environments); difficulty in manufacturing complex shapes (traditional molding methods struggle to produce products with complex internal structures such as porous, hollow, or gradient structures, and subsequent processing (e.g., superstretching) severely restricts geometric freedom). While existing technologies can improve mechanical strength to some extent (e.g., through freeze-thaw cycles, solvent exchange, or small molecule-induced crosslinking), they generally suffer from insufficient resistance to swelling and inadequate mechanical properties in humid or aqueous environments. Wu et al., in their paper "Solvent-Exchange-Assisted Wet Annealing: A New Strategy for Superstrong, Tough, Stretchable, and Anti-Fatigue Hydrogels," pointed out that a solvent exchange-assisted wet annealing strategy can effectively improve the crosslinking density of PVA hydrogels, thereby significantly enhancing mechanical properties. However, these mechanical properties degrade with increasing immersion time in water, limiting their long-term stability in aqueous environments. In their paper "Super-Tough, Non-Swelling Zwitterionic Hydrogel Sensor Based on the Hofmeister Effect for Potential Motion Monitoring of Marine Animals", Ren et al. pointed out that by introducing concentrated sulfuric acid into PVA hydrogel, the internal osmotic pressure of the hydrogel can be effectively improved, giving it both excellent anti-swelling properties and long-term stability in the aquatic environment. However, the mechanical strength of this hydrogel is relatively low, making it difficult to meet the practical application requirements of underwater engineering scenarios.
[0003] 3D printing technology offers a new approach to shaping complex hydrogels, but existing printable hydrogels generally suffer from a trade-off between printability, mechanical properties, and swelling resistance. Achieving both swelling resistance (dimensional stability) and high underwater strength simultaneously is a technological bottleneck in this field, and is of great significance for promoting the practical application of high-performance hydrogels in additive manufacturing technology. Summary of the Invention
[0004] The purpose of this invention is to provide a high-strength and swelling-resistant polyvinyl alcohol hydrogel material and its 3D printing preparation. Through material formulation design modified with a storage modulus enhancer (adapted to the rheological properties of 3D printing) and controlled by a synergistic process of alkali-solvent displacement / salting-out, complex three-dimensional geometries can be manufactured. This method results in a gel composite material with advantages such as high shape controllability, high swelling resistance, and excellent mechanical properties.
[0005] The technical solution of the present invention: A high-strength and swelling-resistant polyvinyl alcohol hydrogel material, directly formed by 3D printing, possesses a high-strength and swelling-resistant synergistic structure, comprising: The matrix material is polyvinyl alcohol, preferably with a high degree of alcoholysis of 98-99%.
[0006] The rheology enhancer, used to adjust the ink storage modulus and printing self-support, and to provide a nano-reinforcing effect, is selected from one or more of the following combinations: cellulose nanofibers (CNF), sodium alginate, chitin nanocrystals, montmorillonite nanosheets, and graphene oxide; more preferably, cellulose nanofibers.
[0007] The solvent system, used to adjust the solubility of PVA and the viscosity of the ink, is deionized water, or a mixture of water, ethanol, and DMSO, with deionized water being more preferred. The volume ratio of water, ethanol, and DMSO is 6–7:1–1.5:1.5–3.
[0008] The high-strength and swelling-resistant polyvinyl alcohol hydrogel material contains 12-20 wt% polyvinyl alcohol; the high-strength and swelling-resistant polyvinyl alcohol hydrogel material contains 1-8 wt% rheology enhancer, preferably 5-7 wt%.
[0009] This high-strength and swelling-resistant polyvinyl alcohol hydrogel material has the following characteristics: Molecular scale: PVA molecular chains recombine after alkaline deprotonation, forming a dense hydrogen bond network and complexation sites; Nanoscale: The uniformly distributed energy storage modulus-enhancing phase forms a physical entanglement or ion complex network with the PVA matrix, with a crystallinity of 25-35%; Meso-macro scale: Complex geometries and programmed structural features imparted by 3D printing processes.
[0010] This high-strength and swelling-resistant polyvinyl alcohol hydrogel material exhibits the following properties in its fully hydrated state: Anti-swelling properties: equilibrium swelling rate -5% to 5%, volume change <5% after 30 days of immersion in pure water or physiological saline, strength retention >95%; Mechanical properties after complete hydration: tensile strength 4-10 MPa, Young's modulus 1-3 MPa; Shape accuracy: Dimensional deviation <5% relative to the design model.
[0011] A 3D printing preparation method for a high-strength and swelling-resistant polyvinyl alcohol hydrogel material includes the following steps: S1: Preparation of 3D printing ink; Polyvinyl alcohol, rheology enhancer and solvent are mixed evenly to obtain an ink with rheological properties adapted to DIW 3D printing; S2: 3D printing; Direct Ink Writing (DIW) technology is used to extrude ink through a nozzle and deposit it along a preset path to obtain a PVA composite hydrogel preform with a designed geometry. The nozzle inner diameter is 0.5-1.5 mm; the extrusion pressure is 0.5-6 MPa; and the printing speed is 3-9 mm / s, preferably 4-7 mm / s.
[0012] Compared to the traditional mold method, the 3D printing process can not only achieve the molding of complex structures, but also more effectively construct the uniform polymer network structure required for reinforcement, thereby better improving the strength and swelling resistance of the final product hydrogel.
[0013] S3: Strong base-induced chain activation and initial crystallization; The PVA composite hydrogel preform is immersed in a strong alkaline solution and treated at room temperature to 40°C for 2-12 hours. The strong alkaline solution is used for PVA chain activation and microcrystal induction, and is selected from one or more combinations of sodium hydroxide (NaOH), potassium hydroxide (KOH), lithium hydroxide (LiOH), and sodium ethoxide (C2H5NaO), with a concentration of 1-7 mol / L, preferably 3-5 mol / L.
[0014] A strong alkaline solution deprotonates the hydroxyl groups of PVA to form PVA-O. - M + This weakens intermolecular hydrogen bonds, introduces ionic interactions, and simultaneously induces the formation of a fine and abundant initial microcrystalline network to achieve further gelation. S4: Immersion in salting-out solution and solvent displacement agent induces densification and enhanced crystallization; The alkali-treated PVA composite hydrogel preform was successively immersed in salting-out solution and solvent displacement agent and treated at room temperature to 60°C for 12-48 hours. Salting-out solution is used for densification and crystallization enhancement, and is selected from one or more of sodium sulfate (Na2SO4), zinc sulfate (ZnSO4), and sodium citrate (C6H5Na3O7) or a mixture of two or more; the concentration of salting-out solution is 0.5 mol / L to 4 mol / L; the treatment time is 2 hours to 24 hours.
[0015] Solvent displacement agents are used for densification and crystallization enhancement, and are selected from one or more of ethanol (C2H5OH), glycerol (C3H8O3), and methanol (CH3OH); the treatment time is 2 hours to 24 hours.
[0016] The salting-out agent induces PVA chain aggregation through the Hofmeister effect / weak solvent-induced phase separation, promoting crystallinity to 25-35%, forming a dense microcrystalline network, and establishing osmotic pressure equilibrium with the external solution. The above process steps cannot be reversed, and the high-strength and swelling-resistant polyvinyl alcohol hydrogel material and its 3D printing preparation method are finally obtained.
[0017] The beneficial effects of this invention are: 1. This invention introduces a rheology enhancer component into the system, which can significantly improve the rheological properties and molding compatibility of PVA substrates, greatly enhancing the material's direct-write 3D printing capabilities. Simultaneously, by precisely controlling the doping ratio and coordinating it with process parameters such as printing rate, extrusion pressure, and curing conditions, it effectively solves the problems of easy collapse, poor molding accuracy, and weak structural shape retention in pure PVA material printing, providing key technical support for the stable printing of complex three-dimensional structures.
[0018] 2. This invention abandons the traditional post-treatment methods of single salting out and solvent replacement, and innovatively introduces a pre-treatment alkali process. This pretreatment method can induce the formation of dense and uniform initial crystal nuclei in the matrix, effectively optimize the crystal growth mode and micro-aggregate structure, significantly improve the crystallinity and structural density of the material, and thus greatly enhance the overall mechanical strength and structural stability of the composite material.
[0019] 3. This invention overcomes the technical bottleneck of traditional PVA-based materials' inability to simultaneously achieve printability, mechanical strength, and swelling resistance by combining the synergistic optimization of the formulation and printing process with the dual technology of alkali treatment-induced dense crystallization. Ultimately, it prepares a composite printing material that combines excellent 3D printing processing performance, high mechanical strength, and good water resistance and swelling resistance, thus broadening the application range of PVA-based functional composite materials in water environments, complex structural devices, and other scenarios. Attached Figure Description
[0020] Figure 1 This is a physical image of the complex 3D printed sample described in the embodiment. Figure 2 Images of the sample before and after immersion in water for 30 days. Figure 3 Here are the SEM images of the samples; where (a) is the surface morphology of the polyvinyl alcohol hydrogel material obtained in Example 6, and (b) is the surface morphology of the polyvinyl alcohol hydrogel material obtained in Example 1. Detailed Implementation
[0021] The specific embodiments of the present invention will be further described below with reference to the accompanying drawings and technical solutions.
[0022] Example 1 1. Recipe: 10g PVA (degree of polymerization 1700, degree of alcoholysis 99%), 1g CNF (relative to PVA), solvents are 35mL deionized water, 5mL ethanol, and 8mL DMSO; 2. Ink preparation: A predetermined amount of PVA powder was added to 40g of a uniform and transparent CNF suspension, and the mixture was heated in a water bath at 95°C and mechanically stirred at a high speed of 5000rpm for 1.5 hours to obtain a CNF / PVA mixed ink with a PVA mass fraction of 20 wt%.
[0023] 3. Direct Writing (DIW): The target model was constructed using Computer-Aided Design (C4D) software, and the printing path was generated using slicing software (Cura). A printing needle with an inner diameter of 1.19 mm was selected, and the extrusion pressure was set to 3 MPa and the printing speed to 6 mm / s. The CNF / PVA mixed hot solution obtained in step (2) was injected into the printing syringe, and the model was printed layer by layer onto a clean glass substrate at room temperature. The sample size was 10 mm. 60 mm 3 mm.
[0024] 4. Alkali treatment: Immerse in 5 mol / L NaOH solution and soak at room temperature for 6 hours; 5. Solvent displacement The gel was immersed in a 2 mol / L Na₂SO₄ solution for 48 hours, followed by immersion in deionized water for 48 hours. This yielded a CNF / PVA composite hydrogel with an enhanced network structure for 3D printing.
[0025] The mechanical properties characterization of the final composite hydrogel obtained in Example 1 showed that its tensile strength was 5.27 MPa, elastic modulus was 2.03 MPa, elongation at break was 668%, and the mechanical properties remained at 99% after 30 days of hydration, indicating that the material has excellent anti-swelling properties. Figure 3 As shown in the right figure, the surface morphology of the material is dense and flat.
[0026] Example 2 (1) Prepare CNF suspension according to step 2(1) in Example 1.
[0027] (2) Prepare the same CNF / PVA mixed ink as in Example 1, 2(2).
[0028] (3) Perform DIW molding according to step 3 in Example 1.
[0029] (4) Change the concentration of sodium hydroxide (NaOH) in Example 14 to 2 mol / L.
[0030] (5) Process according to the requirements of 5 in Example 1.
[0031] The mechanical properties of the CNF / PVA hydrogel obtained in Example 2 were characterized by a tensile strength of 3.61 MPa, an elastic modulus of 1.24 MPa, and an elongation at break of 453%. Compared to Example 1, Example 2, due to the reduced alkali concentration, resulted in decreased coordination between sodium ions and oxygen anions, leading to a reduction in inter-PVA crystallization nucleation sites. This factor significantly limited the improvement in its mechanical strength and fracture toughness. Nevertheless, the hydrogel still exhibits anti-swelling ability.
[0032] Example 3 (1) Prepare CNF suspension according to step 2(1) in Example 1.
[0033] (2) Prepare the same CNF / PVA mixed ink as in Example 1, 2(2).
[0034] (3) Perform DIW molding according to step 3 in Example 1. (4) Perform alkali treatment according to step 4 in Example 1.
[0035] (5) Change the soaking time of 5 in Example 1 to 24 hours in deionized water.
[0036] The mechanical properties of the CNF / PVA hydrogel obtained in Example 3 were characterized by a tensile strength of 3.81 MPa, an elastic modulus of 1.97 MPa, an elongation at break of 510%, and a mechanical strength retention of 93% after 30 days of hydration. Compared to Example 1, the hydrogel did not reach swelling equilibrium due to the reduced soaking time in deionized water, resulting in a looser network.
[0037] Comparative Example 1 Based on Example 1, step 3 is replaced with a mold forming method. Specifically, it is as follows: (1) The same CNF / PVA mixed ink prepared according to step 2 in Example 1 is injected into a polytetrafluoroethylene (PTFE) mold to form a sample with the same size as the three-dimensional printed sample in Example 1.
[0038] The mechanical properties of the CNF / PVA hydrogel obtained in Comparative Example 1 were characterized by a tensile strength of 3.06 MPa, an elastic modulus of 1.95 MPa, and an elongation at break of 560%. Compared to Example 1, the lack of 3D printing in Comparative Example 1 resulted in uneven polymer spreading, significantly limiting the improvement of its mechanical properties. Nevertheless, this hydrogel still exhibits anti-swelling ability.
[0039] Comparative Example 2 Based on Example 1, the CNF weight in the formula was changed to 0.5g, and then the same weight of PVA powder was added, and the mixture was strictly mixed according to Step 2.
[0040] Direct writing: Strictly follow the implementation steps 3 for 3D printing.
[0041] Testing revealed that the CNF / PVA mixed solution obtained in Comparative Example 2 could not meet the requirements for 3D printing. The apparent viscosity of the mixed solution was too low, and the filaments collapsed during the printing process.
[0042] Comparative Example 3 In step 5 of Example 1, instead of using Na2SO4 for densification, the sample is directly immersed in deionized water.
[0043] The mechanical properties of the CNF / PVA hydrogel obtained in Comparative Example 3 were characterized by a tensile strength of 1.57 MPa, an elastic modulus of 0.58 MPa, and an elongation at break of 490%. Compared to Example 1, Comparative Example 3, lacking Na2SO4-induced phase separation, could not achieve densification of the crystalline network, resulting in severely limited mechanical properties. Nevertheless, this hydrogel still possesses anti-swelling ability.
[0044] Comparative Example 4 (1) Prepare CNF suspension according to step 2(1) in Example 1.
[0045] (2) Prepare the same CNF / PVA mixed ink as in Example 1, 2(2).
[0046] (3) Perform DIW molding according to step 3 in Example 1.
[0047] (4) The gel was soaked in Na2SO4 solution for 48 hours.
[0048] (5) Immerse in 5 mol / L NaOH solution and soak at room temperature for 6 h; then soak in deionized water for 48 h.
[0049] The mechanical properties of the CNF / PVA hydrogel obtained in Comparative Example 4 were characterized by a tensile strength of 4.001 MPa, an elastic modulus of 1.10 MPa, an elongation at break of 371.8%, and a mechanical strength retention of 83% after 30 days of water treatment. Compared to Example 1, Comparative Example 4 altered the process sequence, hindering the efficiency of alkali treatment in inducing uniform microcrystals and preventing the densification of the crystalline network, thus severely limiting its mechanical properties.
[0050] Comparative Example 5 In Example 1, the glycerol in 5 was changed to a 2 mol / L sodium sulfate solution.
[0051] Testing revealed that the mechanical properties of the CNF / PVA hydrogel obtained in Comparative Example 4 were not significantly different from those in Example 1, and the hydrogel also exhibited anti-swelling ability.
[0052] Comparative Example 6 The step (4) in Example 1 is changed, and instead of alkali treatment, the sample is directly soaked in deionized water.
[0053] The obtained hydrogel was tested and found to have a tensile strength of 1.06 MPa, an elastic modulus of 0.88 MPa, and an elongation at break of 260%. It does not possess anti-swelling properties. Figure 3 As shown in the left figure, the surface morphology of the material is porous.
Claims
1. A high-strength and swelling-resistant polyvinyl alcohol hydrogel material, characterized in that, This high-strength and swelling-resistant polyvinyl alcohol hydrogel material is directly formed by 3D printing and has a high-strength and swelling-resistant synergistic structure, including: The matrix material is polyvinyl alcohol, and its content in high-strength and swelling-resistant polyvinyl alcohol hydrogel materials is 12-20 wt%. The rheology enhancer is present in the high-strength and swelling-resistant polyvinyl alcohol hydrogel material at a content of 1-8 wt%. The rest are solvents.
2. The high-strength and swelling-resistant polyvinyl alcohol hydrogel material according to claim 1, characterized in that, The rheology enhancer is selected from one or more of the following: cellulose nanofibers, sodium alginate, chitin nanocrystals, montmorillonite nanosheets, and graphene oxide.
3. The high-strength and swelling-resistant polyvinyl alcohol hydrogel material according to claim 1, characterized in that, The solvent is deionized water, or a mixture of water, ethanol, and DMSO, wherein the volume ratio of water, ethanol, and DMSO is 6-7:1-1.5:1.5-3.
4. A method for 3D printing a high-strength and swelling-resistant polyvinyl alcohol hydrogel material, characterized in that, Includes the following steps: S1: Preparation of 3D printing ink; Polyvinyl alcohol, rheology enhancer and solvent are mixed evenly to obtain an ink with rheological properties suitable for direct ink writing technology in 3D printing; S2: 3D printing; Using direct ink writing technology, ink is extruded through a nozzle and deposited along a preset path to obtain a PVA composite hydrogel preform with a designed geometry; Nozzle inner diameter is 0.5-1.5mm; extrusion pressure is 0.5-6 MPa; printing speed is 3-9 mm / s; S3: Strong base-induced chain activation and initial crystallization; The PVA composite hydrogel preform was immersed in a strong alkaline solution and treated at room temperature to 40°C for 2-12 hours. S4: Salting-out solution and solvent displacement agent induce densification and enhanced crystallization; The alkali-treated PVA composite hydrogel preform was successively immersed in a salting-out solution and a solvent displacement agent. The salting-out solution was treated for 12-48 hours at room temperature to 60°C, while the solvent displacement agent was treated for 2-24 hours.
5. The 3D printing preparation method according to claim 4, characterized in that, The strong alkaline solution is one or a combination of two or more of sodium hydroxide, potassium hydroxide, lithium hydroxide, and sodium ethoxide, with a concentration of 1-7 mol / L.
6. The 3D printing preparation method according to claim 4, characterized in that, The salting-out solution is one or more of sodium sulfate, zinc sulfate, and sodium citrate; the concentration of the salting-out solution is 0.5 mol / L to 4 mol / L.
7. The 3D printing preparation method according to claim 4, characterized in that, The solvent displacement agent is one or a mixture of two or more of ethanol, glycerol, and methanol.