Preparation method of high-strength, environment-friendly and conductive composite gel material

Abstract

The invention relates to the technical field of functional gel materials, and discloses a preparation method of a high-strength, environment-friendly and conductive composite gel material, and the composite gel material is prepared from the following components by mass: 10-40% of water; 0.5-8% of zinc bromide; 30-60% of glycerin; 5-20% of ethanol; 0.5-8% of tannic acid; the preparation method comprises the following steps: forming a dynamic hydrogen bond network through the synergistic crosslinking effect of the gelatin and the tannic acid, regulating and controlling the gelation rate in combination with a glycerol-water-ethanol mixed solvent, introducing zinc bromide to improve the conductivity, mixing the components in proportion, heating and stirring, cooling, and quickly curing and forming within 1-2 minutes. The tensile strength of the obtained composite gel material is improved by more than 60 times, the electric conductivity reaches 2-10 S / m, high mechanical strength, rapid prototyping, recoverable remodeling and excellent electric conductivity are achieved through natural polymer crosslinking, solvent volatilization regulation and ionic conductivity enhancement technologies, and the composite gel material has the advantages of being high in mechanical strength, capable of being recycled and remodeled and high in conductivity. The method is suitable for the fields of flexible electronics, wearable equipment and biosensing.

Description

Technical Field

[0001] The invention relates to the technical field of functional gel materials, in particular to a method for preparing a high-strength, environmentally friendly and conductive composite gel material. Background Art

[0002] Traditional gel materials have broad application prospects in many fields. However, the traditional gel materials currently used, such as agarose and polyvinyl alcohol-based gel, have a series of problems that need to be solved. First, in terms of mechanical strength, the tensile strength is less than 0.5 MPa, which makes them prone to deformation or even breakage when subjected to external forces, severely limiting their use in some application scenarios with high strength requirements. Secondly, the slow molding speed is also a major disadvantage. The curing time often exceeds 30 minutes, which not only reduces production efficiency, but also increases production costs, making it difficult to meet the needs of some rapid manufacturing processes. Furthermore, the single function has greatly limited the scope of application of these traditional gel materials and cannot meet the diverse application needs of modern times.

[0003] In order to improve the performance of traditional gel materials, the existing technology mostly uses the method of adding chemical cross-linking agents (such as glutaraldehyde) or synthetic polymers (such as polyacrylamide). However, these methods have obvious defects. On the one hand, the use of chemical cross-linking agents can easily introduce toxic substances, which may bring potential safety hazards to some application scenarios that are in close contact with the human body or organisms, such as the biomedical field. On the other hand, these methods are difficult to achieve green and recyclable materials, which does not meet the requirements of today's society for sustainable development.

[0004] In recent years, dynamic cross-linked gels based on natural polyphenols (such as tannic acid) have attracted widespread attention due to their reversible hydrogen bonding properties. This property gives the gel material a certain self-healing ability, allowing it to recover some of its properties when damaged. However, the mechanical properties of this type of gel material are still insufficient, and the tensile strength is usually less than 1MPa, which is difficult to meet the needs of some practical applications with high strength requirements.

[0005] In addition, in the field of composite gel materials, conventional composite gel materials mostly rely on carbon materials (such as carbon nanotubes) or metal particles to achieve the conductive function. However, these materials have the problem of uneven dispersion, which will lead to unstable conductive properties of gel materials and affect their practical application effects. At the same time, the cost of carbon nanotubes and metal particles is high, which undoubtedly increases the production cost of gel materials and reduces their competitiveness in the market. Summary of the invention

[0006] 1. Technical issues to be resolved

[0007] In view of the shortcomings of the prior art, the present invention provides a method for preparing a high-strength, environmentally friendly, conductive composite gel material, which has the advantages of rapid prototyping, high mechanical strength, recyclability and excellent conductivity, and solves the problems of low mechanical strength, single function and non-recyclability of traditional gel materials.

[0008] (II) Technical solution

[0009] To achieve the above object, the present invention provides the following technical solution: a method for preparing a high-strength, environmentally friendly, conductive composite gel material, comprising the following preparation steps:

[0010] Step 1: Prepare gelatin, glycerol, deionized water, ethanol, tannic acid and zinc bromide in a formula ratio and prepare a mold;

[0011] Step 2: Mix the zinc bromide solution and water according to the formula ratio, and stir and dissolve them for 10-40 minutes at a temperature of 30-70°C using a stirring device to form a dilute zinc bromide solution;

[0012] Step 3: Add glycerol in the formula ratio to the solution in step 2, and continue stirring for 10-20 minutes using a stirring device to form a uniform mixed solution A;

[0013] Step 4: Add tannic acid solution dissolved in ethanol in a formula ratio to the mixed solution A, and stir for 10-30 minutes at room temperature using a stirring device until the solution is completely dissolved to form a mixed solution B;

[0014] Step 5: Add gelatin in a formula ratio to the mixed solution B in step 4, and stir and disperse it for 1-3 hours using a stirring device to obtain a mixed solution C;

[0015] Step 6: Inject the mixed solution C into a pre-prepared mold, let it stand for 1-2 minutes at room temperature for solidification and demoulding to obtain a primary gel;

[0016] Step 7: Soak the primary gel in a sodium citrate solution with a formula ratio for 12-24 hours, take it out, and dry it at a temperature of 65-75° C. for 35-45 minutes to obtain a composite gel material.

[0017] Preferably, the composite gel material is prepared from the following components by mass percentage: gelatin 10-30%; glycerol 30-60%; water 10-40%; ethanol 5-20%; tannic acid 0.5-8%; zinc bromide 0.5-8%.

[0018] Preferably, the gelatin is food grade or medical grade gelatin with a molecular weight of 50-150 kDa and a preferred mass percentage of 15-25%.

[0019] Preferably, the amount of zinc bromide solution added is 1-5% of the total mass, preferably 2-4%.

[0020] Preferably, the ethanol is used as a reaction medium to promote the dissolution of tannic acid.

[0021] Preferably, in step 2, the mass ratio of gelatin to water is 1:2-1:5.

[0022] Preferably, in step 5, zinc bromide is added dropwise in the form of an ethanol solution, and the solution concentration is 5-15wt%.

[0023] Preferably, in step seven, the concentration of the sodium citrate solution is 0.3-0.7 mol / L, and the soaking temperature is 25-40°C.

[0024] Preferably, the composite gel material prepared in step seven can be recycled and reshaped by crushing the waste gel, dissolving it in a 60-80°C water-ethanol mixed solvent with a volume ratio of 1:1-3:1, and reshaping it after adjusting the solid content.

[0025] Preferably, the composite gel material is used in flexible electronic devices, wearable sensors or bioelectrodes.

[0026] Compared with the prior art, the present invention provides a method for preparing a high-strength, environmentally friendly, conductive composite gel material, which has the following beneficial effects:

[0027] 1. The present invention improves the mechanical properties of the composite gel material through the double cross-linking effect of gelatin and tannic acid. Gelatin and tannic acid form a stable double cross-linking network through hydrogen bonds and hydrophobic effects, which significantly improves the tensile strength of the material to a maximum of 20MPa, which is more than 200-10000% higher than that of traditional gelatin-based gels. This high-strength property enables the composite gel material to be used in fields with high requirements for mechanical properties, such as supporting materials for flexible electronic devices and wearable devices.

[0028] 2. The present invention optimizes the solvent ratio of water and ethanol (synergistic effect of water and ethanol) and uses sodium citrate for post-treatment, so that the prepared composite gel material has the advantages of rapid forming and high conductivity. The rapid curing of the composite gel material is achieved by promoting hydrogen bond formation by water and accelerating solvent volatilization by ethanol, so that the curing time is less than 1 hour, and the optimal curing time obtained by testing is only 1 minute for forming. At the same time, using sodium citrate as a post-treatment reagent can further improve the conductive properties of the material, thereby meeting the conductive properties requirements of flexible electronic devices and wearable sensors and expanding the application range of the material.

[0029] 3. The present invention uses the dynamic hydrogen bond network of tannic acid and a reasonable design and ratio of raw materials to prepare a composite gel material with the advantages of excellent recyclability and environmental friendliness. The polyphenolic hydroxyl groups of tannic acid and glycerol form a reversible cross-linking network, thereby giving the material self-healing and recyclability. After three cycles of recycling, the performance retention rate of the test material is still greater than 90%, enabling it to achieve 100% recycling and reshaping. This feature can not only reduce the generation of waste and reduce the pollution pressure on the environment, but also reflect the sustainable development characteristics of the material and conform to the concept of environmental protection. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 A flow chart is prepared for the present invention;

[0031] Figure 2 This is an electrochemical impedance spectrum curve of the gel of the present invention. DETAILED DESCRIPTION

[0032] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0033] See also Figure 1-Figure 2 A method for preparing a high-strength, environmentally friendly, conductive composite gel material. The composite gel material is prepared from the following components by mass percentage: gelatin 10-30%; glycerol 30-60%; water 10-40%; ethanol 5-20%; tannic acid 0.5-8%; zinc bromide 0.5-8%. Gelatin and tannic acid form a double cross-linked network through hydrogen bonds and hydrophobic effects. Zinc bromide is evenly dispersed in the gel matrix. After the material is soaked in sodium citrate solution, the tensile strength is increased by more than 60 times.

[0034] The raw materials of the composite gel material are composed of a matrix, a cross-linking agent, a solvent and a conductive additive;

[0035] Matrix: Glycerol is used in an amount of 40-70 wt%. Glycerol, as a flexible matrix, can not only provide good plasticity for the composite gel material, enabling it to flexibly deform in different application scenarios, but also has excellent biocompatibility and can better integrate with biological systems, and is suitable for biomedical related application fields;

[0036] Cross-linking agent: Tannic acid is used in an amount of 1-10wt%. Tannic acid has abundant polyphenolic hydroxyl groups, which can form a dynamic hydrogen bond network with glycerol. This dynamic hydrogen bond network will give the composite gel material a reorganization property. For example, when subjected to external force, the hydrogen bonds can break and reorganize, thereby giving the material a certain degree of adaptability and buffering capacity.

[0037] Solvent: It is composed of water (dosage is 10-30wt%) and ethanol (dosage is 5-20wt%). Water and ethanol play a regulatory role in the preparation process of the composite gel material. Water can promote the formation of hydrogen bonds and help to build a stable network structure. Ethanol, as a solvent and reaction medium, promotes the dissolution and reaction of tannic acid, which can accelerate the volatilization of the solvent, thereby regulating the gelation rate and structural uniformity to ensure that the composite gel material has a good internal structure and performance stability;

[0038] Conductive additive: zinc bromide is used as a conductive additive, and its dosage is 0.5-5 wt%. Zinc bromide can dissociate into Zn² in the composite gel material. + and Br - Ions, these two ions form a conductive path inside the material, thereby improving the conductive properties of the composite gel material.

[0039] The composite gel material is prepared from the above-mentioned matrix, cross-linking agent, solvent and conductive additive, and the specific steps are as follows:

[0040] (1) First, glycerol, water, and ethanol are mixed in the above proportions and stirred for 10-30 min at a temperature of 60-80°C to allow the three substances to be fully mixed to form a uniform solution. During this process, appropriate temperature and stirring time help to evenly disperse the components, laying a good foundation for subsequent reactions.

[0041] The advantages are: water in the system can promote the formation of hydrogen bonds and provide support for the composite gel material to build a stable structure; ethanol can accelerate the volatilization of the solvent. Through the synergistic effect of the two, the rapid molding of the composite gel material can be achieved, and the curing time is less than 2 hours. This rapid molding feature can improve production efficiency while reducing production costs.

[0042] (2) Next, tannic acid powder is added to the above homogenous solution and stirring is continued for 1-2 hours until the tannic acid is completely dissolved to form a pre-crosslinking system. At this stage, the polyphenolic hydroxyl groups of tannic acid begin to interact with the hydroxyl groups of glycerol to initially form the prototype of a dynamic hydrogen bond network;

[0043] The advantages are: the polyphenolic hydroxyl groups of tannic acid and the hydroxyl groups of glycerol form reversible cross-links. This reversible cross-linking mechanism enables hydrogen bonds to be reformed under certain conditions when the material is damaged, thereby giving the material self-healing properties. In addition, during the recycling process, the hydrogen bond network can be destroyed under appropriate conditions, achieving material recycling and reshaping to improve the sustainable utilization of the material.

[0044] (3) Then, zinc bromide ethanol solution (concentration of 5-15wt%) is added dropwise. After addition, dispersion treatment is performed for 30-60 minutes to ensure that zinc bromide can be evenly dispersed in the pre-crosslinking system, so as to ensure that the ions dissociated from zinc bromide can be evenly distributed in the subsequent curing process to form a continuous conductive path;

[0045] The advantages are: zinc bromide is evenly dispersed in the composite gel material and dissociates to form continuous ion channels. The ion channels provide an effective pathway for the conduction of charges, so that the conductivity of the composite gel material can reach 2.69S / m, thereby meeting the requirements for the conductivity of the composite gel material in practical applications of flexible electronic devices, wearable sensors or bioelectrodes.

[0046] (4) Finally, the mixed liquid is injected into a mold and allowed to stand and solidify at a temperature of 25-40°C for 0.5-2 hours. After the solidification is completed, demolding is performed to obtain a glycerol-tannic acid-zinc bromide composite gel material.

[0047] The composite gel material prepared by the method of the present invention and the gel material prepared by the traditional method in the warehouse were tested for tensile strength and conductivity, and the following Table 1 was obtained:

[0048] Table 1 Tensile strength and conductivity test table

[0049] Material Name Tensile strength (MPa) Electrical conductivity (S / m) Curing time (h) Glycerol-tannic acid-zinc bromide composite gel material of the present invention 0.50 - 20.00 2.69 ≤2.00（0.5-2.00） Traditional Gelatin-Based Gels 0.01 - 1.00 0.01 >2.00

[0050] The composite gel material prepared by the present invention was tested for recovery performance, and the following Table 2 was obtained:

[0051] Table 2 Recycling performance data

[0052] Cycle times Performance retention rate (%) 1 90 - 100 2 90 - 100 3 90 - 100

[0053] The advantages are: the tensile strength of the high-strength gelatin-based composite gel material prepared by the present invention is 0.50-20 MPa. Compared with traditional gelatin-based gel, its tensile strength is increased by more than 200-10000%, which shows that the composite gel material has better resistance when subjected to external tensile force, and can be applied to some fields with high requirements on mechanical properties. At the same time, the conductivity of the composite gel material can reach up to 2.69S / m. This good conductivity can meet the needs of wearable devices and flexible sensors, and the composite gel material has excellent recyclability and can be 100% recycled and reshaped. After three cycles of recycling, the performance retention rate of the composite gel material is still greater than 90%, which can not only reduce the generation of waste, but also reduce the pressure on the environment, thereby reflecting the sustainable development characteristics of the material.

[0054] Example 1

[0055] Step 1: Prepare gelatin, glycerol, deionized water, ethanol, tannic acid and zinc bromide in a formula ratio and prepare a mold;

[0056] Step 2: Mix the zinc bromide solution and water according to the formula ratio, and stir and dissolve them at 60° C. for 35 minutes using a stirring device to form a dilute zinc bromide solution;

[0057] Step 3: Add glycerol in the formula ratio to the solution in step 2, and continue stirring for 15 minutes using a stirring device to form a uniform mixed solution A;

[0058] Step 4: Add tannic acid solution dissolved in ethanol in a formula ratio to the mixed solution A, and stir for 15 minutes at room temperature using a stirring device until the solution is completely dissolved to form a mixed solution B;

[0059] Step 5: Add gelatin in a formula ratio to the mixed solution B in step 4, and stir and disperse it for 2 hours using a stirring device to obtain a mixed solution C;

[0060] Step 6: Inject the mixed solution C into a pre-prepared mold, let it stand for 1 minute at room temperature for solidification and demoulding to obtain a primary gel;

[0061] Step 7: Soak the primary gel in a sodium citrate solution with a formula ratio for 16 hours, take it out, and dry it at 70° C. for 40 minutes to obtain a composite gel material.

[0062] Comparative Example 1 (without gelatin)

[0063] (1) In this comparative example, gelatin was not added, and the other raw materials were the same as those in the example. In the mixing step, water, glycerol and ethanol were directly mixed in corresponding proportions. It was found through testing that gelatin played an important role in cross-linking and supporting in the gel formation process. After omitting gelatin, the system lacked the necessary network structure forming substances.

[0064] (2) The subsequent steps were carried out according to Example 1, but the final product could not be formed. This shows that gelatin has a crucial influence on the formation and performance of the gel. It can interact with other ingredients to form a stable three-dimensional network structure, thereby giving the gel a certain shape and mechanical properties.

[0065] Comparative Example 2 (without sodium citrate treatment)

[0066] (1) Gel was prepared according to steps 1 to 7 of Example 1, omitting the treatment process of sodium citrate solution in step 7, and studying the effect of sodium citrate treatment on gel properties alone;

[0067] (2) The obtained gel was subjected to performance testing, and the results showed that its tensile strength was 0.8 MPa and its conductivity was 8 S / m. Compared with the results of Example 1, it can be seen that sodium citrate treatment has an improvement effect on the mechanical properties and conductive properties of the gel.

[0068] Comparative Example 3 (Ethanol ratio is too low)

[0069] (1) Adjust the amount of each component, specifically 15g of gelatin, 40g of water, 40g of glycerol, and 5g of ethanol. Ethanol not only acts as a solvent in the system, but also affects the curing rate and structure of the gel. Reducing the proportion of ethanol will change the physical properties and reaction kinetics of the system.

[0070] (2) Following the subsequent steps of Example 1, it was found that after the curing time was extended to 10 min, the tensile strength became 35 MPa. This indicates that the proportion of ethanol affects the curing time and mechanical properties of the gel. Therefore, a suitable proportion of ethanol is helpful to achieve rapid molding and improve the mechanical strength of the gel.

[0071] The gel material obtained by the present invention is tested for performance in the following manner, specifically:

[0072] Standard sample preparation: Gel samples were prepared using the methods described in the above examples and comparative examples. For the tensile strength test, samples of appropriate size were prepared to ensure the accuracy and comparability of the test results.

[0073] Tensile strength test: Use a professional tensile testing machine to perform a tensile test on the prepared standard tensile mechanics specimen, and set the tensile rate to an appropriate value (e.g., 2 mm / min) to accurately measure the tensile strength of the gel material;

[0074] Conductivity test: Use a suitable conductivity measuring instrument to measure the conductivity of the gel material, ensuring the consistency of the measurement environment and conditions to obtain accurate conductivity data;

[0075] Recycling performance test: The gel material was recycled and reshaped multiple times, and its tensile strength was measured after each recycling, and the strength retention rate was calculated to evaluate the recycling performance of the material.

[0076] The following is the specific test results Table 3:

[0077] Table 3

[0078] Material Type Tensile strength (MPa) Electrical conductivity (S / m) Curing time (min) Number of recycling times (strength retention rate) Example 1 50.2±1.5 9.8±0.3 1 3 times (88%) Comparative Example 1 (without gelatin) - - - - Comparative Example 2 (untreated) 0.8±0.2 8.1±0.4 1 - Comparative Example 3 (Low Ethanol) 35.6±2.1 7.5±0.2 10 3 times (82%)

[0079] From the data analysis in Table 3 above, we can conclude that:

[0080] The present invention can successfully prepare a gel material with high mechanical strength (up to 50 MPa), rapid molding (only 1 min) and high conductivity (close to 10 S / m) by means of gelatin-tannic acid double cross-linking, solvent ratio optimization and sodium citrate post-treatment. It can be clearly seen from the comparison results of the embodiment and the comparative example that the addition of gelatin will affect the molding of the gel, the treatment of sodium citrate can effectively improve the mechanical properties and conductivity of the gel, and the appropriate ethanol ratio is helpful to achieve rapid molding and improve the comprehensive performance of the gel. The gel material prepared according to the method of the present invention has broad application prospects in the field of flexible electronics, for example, it can be used to prepare flexible sensors and wearable devices.

[0081] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the appended claims and their equivalents.

Claims

1. A method for preparing a high-strength, environmentally friendly, conductive composite gel material, characterized in that: The method comprises the following preparation steps: Step 1: Prepare gelatin, glycerol, deionized water, ethanol, tannic acid and zinc bromide in a formula ratio and prepare a mold; Step 2: Mix the zinc bromide solution and water according to the formula ratio, and stir and dissolve them for 10-40 minutes at a temperature of 30-70°C using a stirring device to form a dilute zinc bromide solution; Step 3: Add glycerol in the formula ratio to the solution in step 2, and continue stirring for 10-20 minutes using a stirring device to form a uniform mixed solution A; Step 4: Add tannic acid solution dissolved in ethanol in a formula ratio to the mixed solution A, and stir for 10-30 minutes at room temperature using a stirring device until the solution is completely dissolved to form a mixed solution B; Step 5: Add gelatin in a formula ratio to the mixed solution B in step 4, and stir and disperse it for 1-3 hours using a stirring device to obtain a mixed solution C; Step 6: Inject the mixed solution C into a pre-prepared mold, let it stand for 1-2 minutes at room temperature for solidification and demoulding to obtain a primary gel; Step 7: Soak the primary gel in a sodium citrate solution with a formula ratio for 12-24 hours, take it out, and dry it at a temperature of 65-75° C. for 35-45 minutes to obtain a composite gel material.

2. The method for preparing a high-strength, environmentally friendly, conductive composite gel material according to claim 1, characterized in that: The composite gel material is prepared from the following components by mass percentage: 10-30% gelatin; 30-60% glycerol; 10-40% water; 5-20% ethanol; 0.5-8% tannic acid; and 0.5-8% zinc bromide.

3. The method for preparing a high-strength, environmentally friendly, conductive composite gel material according to claim 1, characterized in that: The gelatin is food grade or medical grade gelatin with a molecular weight of 50-150 kDa and a preferred mass percentage of 15-25%.

4. The method for preparing a high-strength, environmentally friendly, conductive composite gel material according to claim 1, characterized in that: The amount of zinc bromide added is 1-5% of the total mass, preferably 2-4%.

5. The method for preparing a high-strength, environmentally friendly, conductive composite gel material according to claim 1, characterized in that: The ethanol serves as a reaction medium to promote the dissolution of tannic acid.

6. The method for preparing a high-strength, environmentally friendly, conductive composite gel material according to claim 1, characterized in that: In the step three, the mass ratio of gelatin to solvent is 1:2-1:

5.

7. The method for preparing a high-strength, environmentally friendly, conductive composite gel material according to claim 1, characterized in that: In the step 4, tannic acid is added dropwise in the form of an ethanol solution, and the solution concentration is 5-15wt%.

8. The method for preparing a high-strength, environmentally friendly, conductive composite gel material according to claim 1, characterized in that: The concentration of the sodium citrate solution in step seven is 0.5-2 mol / L.

9. The method for preparing a high-strength, environmentally friendly, conductive composite gel material according to claim 1, characterized in that: The composite gel material prepared in step seven can be recycled and reshaped by crushing the waste gel, dissolving it in a 60-80°C water-ethanol mixed solvent with a volume ratio of 1:1-3:1, and adjusting the solid content before reshaping.

10. The method for preparing a high-strength, environmentally friendly, conductive composite gel material according to claim 1, characterized in that: The composite gel material is applied to flexible electronic devices, wearable sensors or bioelectrodes.

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