CN111875908A - Self-healing aerogel - Google Patents
Self-healing aerogel Download PDFInfo
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- CN111875908A CN111875908A CN202010712613.3A CN202010712613A CN111875908A CN 111875908 A CN111875908 A CN 111875908A CN 202010712613 A CN202010712613 A CN 202010712613A CN 111875908 A CN111875908 A CN 111875908A
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Abstract
The invention relates to the field of aerogels, in particular to a self-healing aerogel, which is prepared by the following steps: mixing a biomass polysaccharide solution with the mass fraction of less than or equal to 5 wt% and a polyvinyl alcohol aqueous solution with the mass fraction of 5 wt% -20 wt% according to the weight ratio of 100: (15-35) preparing a composite hydrogel material by mixing according to the mass ratio, and then freezing and drying the composite hydrogel material to obtain the self-healing aerogel; wherein the polyvinyl alcohol has an average degree of polymerization of 1000-2000. The self-healing aerogel provided by the invention can show excellent mechanical properties under very low apparent density under the interaction of ionic bonds and hydrogen bonds, has the capability of fast self-healing at room temperature, has good mechanical properties before and after self-healing, can be completely dissolved, has good biocompatibility, is environment-friendly and nontoxic to human bodies.
Description
Technical Field
The invention relates to the field of aerogels, in particular to a self-healing aerogel.
Background
Aerogels, also known as xerogels, are a solid material in the form of a least dense solid, about 3 kilograms per cubic meter. The general aerogel is a silica aerogel, and the types of aerogels include silica-based, carbon-based, sulfur-based, metal oxide-based, metal-based, and the like, and any aerogel can be called aerogel as long as it can be dried to remove the internal solvent, and can substantially maintain its shape, and the product has high porosity and low density.
Aerogel as a nano porous material with a controllable structure has the unique advantages of high specific surface area, adjustable pore diameter, adjustable framework, special surface performance and the like, and in recent years, the application of the aerogel in various high-tech fields such as adsorption, catalysis, sensors, thermal insulators, electrodes, biotechnology and the like is more and more emphasized.
However, the aerogel has relatively poor mechanical strength and is fragile compared with a massive solid material due to the random through three-dimensional network structure, and in practical application, the aerogel is inevitably subjected to irreparable mechanical damage, so that the structural integrity and inherent performance of the aerogel are damaged.
It is now increasingly recognized that the key to extending the useful life of aerogels is to obtain self-healing capabilities. Therefore, it is essential to develop aerogels with self-healing properties that recover structural integrity and inherent properties after damage.
Disclosure of Invention
Therefore, the technical problem to be solved by the present invention is to overcome the defects that the aerogel in the prior art inevitably suffers from irreparable mechanical damage in practical application, so that the structural integrity and inherent performance of the aerogel are damaged, and the service life of the aerogel is short, so as to provide a self-healing aerogel.
In order to solve the technical problems, the technical scheme adopted by the invention is as follows:
a self-healing aerogel is prepared by the following steps:
mixing a biomass polysaccharide solution with the mass fraction of less than or equal to 5 wt% and a polyvinyl alcohol aqueous solution with the mass fraction of 5 wt% -20 wt% according to the weight ratio of 100: (15-35) preparing a composite hydrogel material by mixing according to the mass ratio, and then freezing and drying the composite hydrogel material to obtain the self-healing aerogel;
wherein the polyvinyl alcohol has an average degree of polymerization of 1000-2000.
Further, the biomass polysaccharide is at least one of chitosan and sodium alginate.
Further, the biomass polysaccharide solution is a chitosan solution, and the chitosan solution is prepared from chitosan powder with the deacetylation degree of 65-90% and a dilute acid solution.
Further, the dilute acid solution is an acetic acid solution.
Further, the mass fraction of the acetic acid solution is 1-5%.
Further, the raw materials for preparing the composite hydrogel material also comprise a zwitterionic polyurethane aqueous solution with the mass fraction of 5 wt% -20 wt%.
Further, the adding mass ratio of the biomass polysaccharide solution to the zwitterionic polyurethane aqueous solution to the polyvinyl alcohol aqueous solution is 100: (1-10): (15-35).
Furthermore, the zwitterionic polyurethane aqueous solution is prepared by mixing N, N-dihydroxyethyl isonicotine, hexamethylene diisocyanate and 1, 3-propane sultone.
Further, the preparation of the zwitterionic polyurethane aqueous solution comprises the following steps:
reacting N, N-dihydroxyethyl isonicotinite, hexamethylene diisocyanate and a catalyst in an organic solvent at the temperature of 80 ℃ for 3-5 hours to synthesize shape memory polyurethane, adding 1, 3-propane sultone, carrying out ring opening reaction at the temperature of 50 ℃ for more than 6 hours to obtain a mixed solution of zwitterionic polyurethane and the organic solvent, removing the organic solvent to obtain zwitterionic polyurethane, and dissolving the zwitterionic polyurethane in water to obtain a zwitterionic polyurethane aqueous solution.
Further, the organic solvent is at least one of N, N-dimethylformamide, N-dimethylacetamide, tetrahydrofuran and dimethyl sulfoxide, and/or the catalyst is a dibutyltin dilaurate catalyst.
Further, the removing of the organic solvent includes a step of drying the mixed solution of the zwitterionic polyurethane and the organic solvent at 80 ℃ for 24 hours.
Further, the preparation of the composite hydrogel material comprises the following steps:
uniformly mixing the raw materials of the composite hydrogel material, and ultrasonically mixing for 10-30 minutes to remove bubbles to obtain a mixed solution;
freezing the mixed solution at-50-0 ℃ for 10-20 h;
unfreezing the frozen mixed solution at room temperature for 1-5 h;
repeating the freezing-unfreezing operation for 1-5 times to obtain the composite hydrogel material.
Further, the step of freeze-drying the composite hydrogel material to obtain the self-healing aerogel comprises the step of carrying out vacuum freeze-drying or supercritical drying on the composite hydrogel material.
Further, the vacuum freeze-drying comprises the following steps: and (3) placing the composite hydrogel material in a vacuum environment with the pressure of less than 5Pa, and freeze-drying for 12-48h at-55 ℃.
Further, the supercritical drying comprises the following steps: the method comprises the steps of pre-filling 2MPa of nitrogen into a reactor by taking ethanol as a supercritical drying medium, heating to 260 ℃ at a heating rate of 50 ℃/h, keeping the temperature for 2h, slowly releasing pressure at a speed of 2MPa/h until the pressure is zero, filling nitrogen for 10-30 min to remove residual ethanol in the reactor, and pumping the obtained aerogel until the pressure is less than 5Pa and the time is 12-48h when the temperature is slowly reduced to the room temperature.
The technical scheme of the invention has the following advantages:
1. the self-healing aerogel provided by the invention has the advantages that the raw materials for preparing the self-healing aerogel and the preparation method are limited, so that a dissolving phenomenon can occur to a molecular chain at the cut of the prepared aerogel under the action of water, then anions and cations at two ends of the cut of the aerogel can move in the dissolved part, the molecular chain can be reconnected under the electrostatic action of ionic bonds, meanwhile, hydrogen bonds and the ionic bonds generate a synergistic action to heal the cut, and the self-healing of the aerogel is realized, namely the self-healing aerogel provided by the invention can also show excellent mechanical properties under very low apparent density under the interaction of the ionic bonds and the hydrogen bonds, has the capability of fast self-healing at room temperature, has good mechanical properties before and after self-healing, can be completely dissolved and has good biocompatibility, is environment-friendly and nontoxic to human body, and can be widely applied to the fields of medical care, textile and clothing, catalysis, aerospace, unmanned driving, heat insulation foam, oil stain absorption or dust particle absorption and the like.
2. According to the self-healing aerogel provided by the invention, the mechanical property and the self-healing property of the generated self-healing aerogel can be controlled by adjusting different proportions of the polyvinyl alcohol aqueous solution, the zwitterionic polyurethane aqueous solution and the chitosan solution so as to meet the requirements of aerogels in different fields.
3. According to the self-healing aerogel provided by the invention, chitosan and polyvinyl alcohol are selected as preparation raw materials, wherein the chitosan is derived from waste shrimp shells and crab shells and has the characteristic of low cost, and the vinyl polymer is a compound which can be used as a carbon source and an energy source by bacteria and has the characteristics of biodegradability, low price and the like.
4. According to the self-healing aerogel provided by the invention, the deacetylation degree is the ratio of the number of deacetylated glucosamine units to the total number of glucosamine units, one of the most basic structural parameters of chitosan is considered, the higher the deacetylation degree is, the more free amino groups on a molecular chain are, the better the solubility in acid is, the water absorption rate of chitosan is controlled by limiting the deacetylation degree of chitosan, the water absorption rate of chitosan is increased along with the increase of the deacetylation degree, and the increase of the water absorption rate is beneficial to the improvement of the self-healing effect.
5. According to the self-healing aerogel provided by the invention, by adding the zwitterionic polyurethane aqueous solution, as the zwitterionic polyurethane has super strong biological pollution resistance and excellent biocompatibility, and as super strong electrostatic acting force, a water layer can be formed on the surface of a material by the zwitterionic polymer, so that the self-healing performance of the self-healing aerogel is enhanced.
6. According to the self-healing aerogel provided by the invention, the preparation raw materials of the zwitterion polyurethane aqueous solution are limited, so that the prepared amphoteric polyurethane aqueous solution is low in toxicity, and the self-healing aerogel meets the characteristics of environmental protection.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, and it is obvious that the drawings in the following description are some embodiments of the present invention, and other drawings can be obtained by those skilled in the art without creative efforts.
Fig. 1 is a microscopic structure view of a self-healing aerogel according to example 1 of the present invention;
fig. 2 is a microscopic structure view of the self-healing aerogel according to example 2 of the present invention;
FIG. 3 is a microstructure view of a self-healing aerogel according to example 3 of the present invention;
FIG. 4 is a microstructure diagram of a self-healing aerogel according to example 4 of the present invention;
fig. 5 (left) is a diagram showing the heat insulating effect of the self-healing aerogel according to example 1 of the present invention;
fig. 5 (right) is a diagram showing the heat insulating effect of the self-healing aerogel according to example 2 of the present invention;
FIG. 6 is a graph of the mechanical strength at 70% compressive strain of the self-healing aerogels of examples 1-4 of the present invention;
FIG. 7 is a schematic view of a microscopic self-healing process of the self-healing aerogel according to example 2 of the present invention;
fig. 8 is a tensile stress-strain diagram before and after self-healing of the self-healing aerogel of example 2 of the present invention.
Detailed Description
The following examples are provided to further understand the present invention, not to limit the scope of the present invention, but to provide the best mode, not to limit the content and the protection scope of the present invention, and any product similar or similar to the present invention, which is obtained by combining the present invention with other prior art features, falls within the protection scope of the present invention.
The examples do not show the specific experimental steps or conditions, and can be performed according to the conventional experimental steps described in the literature in the field. The reagents or instruments used are not indicated by manufacturers, and are all conventional reagent products which can be obtained commercially.
The invention relates to a self-healing aerogel, which is prepared by the following steps:
mixing a biomass polysaccharide solution with the mass fraction of less than or equal to 5 wt% and a polyvinyl alcohol aqueous solution with the mass fraction of 5 wt% -20 wt% according to the weight ratio of 100: (15-35) preparing a composite hydrogel material by mixing according to the mass ratio, and then freezing and drying the composite hydrogel material to obtain the self-healing aerogel;
wherein the polyvinyl alcohol has an average degree of polymerization of 1000-2000.
Specifically, the polyvinyl alcohol aqueous solution is prepared according to the following steps: weighing a certain amount of polyvinyl alcohol, adding deionized water according to the final mass fraction, heating and stirring in a water bath kettle at 80 ℃ for 1.5h to fully dissolve polyvinyl alcohol particles, standing in the water bath kettle at 60 ℃ for 0.5h, removing bubbles and preserving heat.
Optionally, the biomass polysaccharide is at least one of chitosan and sodium alginate
When the biomass polysaccharide solution is chitosan solution, the chitosan solution is prepared from chitosan powder with the deacetylation degree of 65-90% and dilute acid solution.
Preferably, the dilute acid solution is selected to be an acetic acid solution. The addition of acetic acid can protonate chitosan, so that the chitosan is promoted to be dissolved in water, and meanwhile, the acetic acid and the chitosan can form an ionic bond, so that the self-healing performance of the aerogel is enhanced.
Specifically, the mass fraction of the acetic acid solution is 1-5%. Too low concentration of acetic acid can lead to incomplete dissolution of the chitosan solution, and too high concentration of acetic acid can lead to small solubility of chitosan in the chitosan solution, thus leading to precipitation of chitosan and failure to prepare aerogel.
Specifically, the chitosan solution is prepared according to the following steps: adding chitosan powder into dilute acid solution at normal temperature, stirring, filtering to remove insoluble substances, and storing at room temperature for later use.
Preferably, in order to enhance the self-healing capability of the self-healing aerogel, a zwitterionic polyurethane aqueous solution with the mass fraction of 5 wt% -20 wt% can be added during the preparation of the composite hydrogel material.
Specifically, the adding mass ratio of the biomass polysaccharide solution to the zwitterionic polyurethane aqueous solution to the polyvinyl alcohol aqueous solution is 100: (1-10): (15-35).
Preferably, in order to reduce the toxicity of the zwitterionic polyurethane aqueous solution, the zwitterionic polyurethane aqueous solution is prepared by mixing N, N-dihydroxyethyl isonicotin, hexamethylene diisocyanate and 1, 3-propane sultone.
The preparation method of the zwitterionic polyurethane aqueous solution specifically comprises the following steps:
reacting N, N-dihydroxyethyl isonicotinite, hexamethylene diisocyanate and a catalyst in an organic solvent at the temperature of 80 ℃ for 3-5 hours to synthesize shape memory polyurethane, adding 1, 3-propane sultone, carrying out ring opening reaction at the temperature of 50 ℃ for more than 6 hours to obtain a mixed solution of zwitterionic polyurethane and the organic solvent, removing the organic solvent to obtain zwitterionic polyurethane, and dissolving the zwitterionic polyurethane in water to obtain a zwitterionic polyurethane aqueous solution.
Wherein the organic solvent is at least one of N, N-dimethylformamide, N-dimethylacetamide, tetrahydrofuran and dimethyl sulfoxide; the catalyst is preferably dibutyltin dilaurate catalyst.
The removal of the organic solvent includes the step of drying the mixed solution of the zwitterionic polyurethane and the organic solvent at 80 ℃ for 24 hours. Specifically, the organic solvent removal comprises pouring the mixed solution of the zwitterionic polyurethane and the organic solvent into a polytetrafluoroethylene disc, and drying for 24 hours in an air-blast drying oven at 80 ℃.
The preparation of the composite hydrogel comprises the following steps: uniformly mixing a polyvinyl alcohol aqueous solution, a zwitterionic polyurethane aqueous solution and a chitosan solution, and then ultrasonically mixing for 10-30 minutes to remove bubbles to obtain a mixed solution; freezing the mixed solution at-50 deg.C-0 deg.C for 10-20 h; unfreezing the frozen mixed solution at room temperature for 1-5 h; repeating the freezing-unfreezing operation for 1-5 times to obtain the composite hydrogel material.
When the composite hydrogel is prepared, the mixed solution with bubbles removed is poured into a specific mould, and then the mould and the mixed solution are frozen and unfrozen together.
As an alternative embodiment, the freeze-drying is at least one of vacuum freeze-drying and supercritical drying.
Wherein, the vacuum freeze drying comprises the following steps: and (3) placing the composite hydrogel material in a vacuum environment with the pressure of less than 5Pa, and freeze-drying for 12-48h at-55 ℃.
The vacuum freeze-drying step may be carried out in a vacuum freeze-dryer.
The supercritical drying comprises the following steps: the method comprises the steps of pre-filling 2MPa of nitrogen into a reactor by taking ethanol as a supercritical drying medium, heating to 260 ℃ at a heating rate of 50 ℃/h, keeping the temperature for 2h, slowly releasing pressure at a speed of 2MPa/h until the pressure is zero, filling nitrogen for 10-30 min to remove residual ethanol in the reactor, and pumping the obtained aerogel until the pressure is less than 5Pa and the time is 12-48h when the temperature is slowly reduced to the room temperature.
The reactor may optionally be in a supercritical autoclave.
The aerogel prepared according to the scheme has ionic bonds and hydrogen bonds, so that under the interaction of the ionic bonds and the hydrogen bonds, the aerogel has excellent self-healing performance and mechanical performance.
Example 1
The embodiment relates to a self-healing aerogel, which is prepared by the following steps:
s1, preparing a polyvinyl alcohol aqueous solution: weighing 18.25g of polyvinyl alcohol, adding 131.25g of deionized water, heating and stirring for 0.5h in a water bath kettle at 40 ℃, heating and stirring for 0.5h when the temperature of the water bath kettle is raised to 60 ℃, heating and stirring for 1h when the temperature of the water bath kettle is raised to 80 ℃, heating and stirring for more than 6h when the temperature of the water bath kettle is raised to 96 ℃, fully dissolving PVA particles, standing for 0.5h in a water bath kettle at 80 ℃, removing bubbles, preserving heat, and preparing a polyvinyl alcohol aqueous solution with the mass fraction of 12.5%;
s2, preparing a chitosan solution: weighing 4g of chitosan powder with deacetylation degree of 85%, weighing 96g of acetic acid with mass fraction of 1%, adding the chitosan powder into an acetic acid aqueous solution at normal temperature, stirring, filtering out insoluble substances, preparing to obtain a chitosan solution with mass fraction of 2%, and storing at room temperature for later use;
s3, preparation of the composite hydrogel material: taking 4g of polyvinyl alcohol aqueous solution prepared in S1 and 16g of chitosan solution prepared in S2, uniformly mixing the polyvinyl alcohol aqueous solution and the chitosan solution, carrying out ultrasonic treatment for 15 minutes to remove bubbles in the solution to obtain a mixed solution, pouring the mixed solution into a mold, putting the mold into a refrigerator, freezing at-30 ℃ for 5 hours, taking out the mold, standing at room temperature for thawing for 2 hours, and repeating the freezing-thawing operation for 3 times to obtain the composite hydrogel.
S4, freeze drying: and (3) placing the composite hydrogel obtained in the step (S3) into a freeze dryer with a cold trap temperature stabilized at-55 ℃ for pre-cooling, placing the pre-cooled aerogel into an iron disc of the freeze dryer after 2 hours, starting a vacuum pump to pump until the pressure is less than 5Pa, and freeze-drying for 24 hours to obtain the CPA-20 self-healing aerogel.
The aerogel obtained by the method can self-heal a heavy object which is 4000 times of the self weight within 60s, the mechanical strength under 70% compressive strain is 0.46MPa, the gaps are uniform, and the heat conductivity coefficient is 0.046W/mk. The microstructure of the aerogel is shown in figure 1.
Example 2
The embodiment relates to a self-healing aerogel, which is prepared by the following steps:
s1, preparing a polyvinyl alcohol aqueous solution: weighing 18.25g of polyvinyl alcohol, adding 131.25g of deionized water, heating and stirring for 0.5h in a water bath kettle at 40 ℃, heating and stirring for 0.5h when the temperature of the water bath kettle is raised to 60 ℃, heating and stirring for 1h when the temperature of the water bath kettle is raised to 80 ℃, heating and stirring for more than 6h when the temperature of the water bath kettle is raised to 96 ℃, fully dissolving PVA particles, standing for 0.5h in a water bath kettle at 80 ℃, removing bubbles, preserving heat, and preparing a polyvinyl alcohol aqueous solution with the mass fraction of 12.5%;
s2, preparing a chitosan solution: weighing 4g of chitosan powder with deacetylation degree of 85%, weighing 96g of acetic acid with mass fraction of 1%, adding the chitosan powder into an acetic acid aqueous solution at normal temperature, stirring, filtering out insoluble substances, preparing to obtain a chitosan solution with mass fraction of 2%, and storing at room temperature for later use;
s3, preparing a zwitterionic polyurethane aqueous solution: reacting N, N-dihydroxyethyl isonicotinite (BINA), Hexamethylene Diisocyanate (HDI) and a catalyst in an organic solvent at 80 ℃ for 3-5 hours to synthesize shape memory polyurethane, then adding 1, 3-propane sultone (1,3-PS) to perform ring-opening reaction at 50 ℃ for more than 6 hours to obtain a mixed solution of zwitterionic polyurethane and the organic solvent, pouring the solution into a polytetrafluoroethylene disc, drying for 24 hours in an air-blast drying oven at 80 ℃, removing the organic solvent to obtain the zwitterionic polyurethane, finally dissolving part of the zwitterionic polyurethane in water, and preparing to obtain a zwitterionic polyurethane aqueous solution with the mass fraction of 10 wt%. Wherein the organic solvent is N, N-dimethylformamide, and the catalyst is dibutyltin dilaurate catalyst.
S4, preparation of the composite hydrogel: taking 4g of polyvinyl alcohol aqueous solution prepared in S1, 16g of chitosan solution prepared in S2 and 1g of zwitterionic polyurethane aqueous solution prepared in S3, uniformly mixing the polyvinyl alcohol aqueous solution, the chitosan solution and the zwitterionic polyurethane aqueous solution, performing ultrasonic treatment for 15 minutes to remove air bubbles in the solution to obtain a mixed solution, pouring the mixed solution into a mold, putting the mold into a refrigerator, freezing for 5 hours at-30 ℃, taking out the mold, standing for thawing for 2 hours at room temperature, and repeating the freezing-thawing operation for 3 times to obtain the composite hydrogel.
S5, freeze drying: and (3) placing the composite hydrogel obtained in the step (S4) into a freeze dryer with a cold trap temperature stabilized at-55 ℃ for pre-cooling, placing the pre-cooled aerogel into an iron disc of the freeze dryer after 2 hours, starting a vacuum pump to pump until the pressure is less than 5Pa, and freeze-drying for 24 hours to obtain the ZCPA-20 self-healing aerogel.
The aerogel obtained by the method can self-heal a heavy object which is 6000 times of the self weight within 60s, the mechanical strength under 70% compressive strain is 0.6MPa, the gaps are uniform, and the heat conductivity coefficient is 0.049W/mk. The microstructure of the aerogel is shown in figure 2.
Example 3
The embodiment relates to a self-healing aerogel, which is prepared by the following steps:
s1, preparing a polyvinyl alcohol aqueous solution: weighing 18.25g of polyvinyl alcohol, adding 131.25g of deionized water, heating and stirring for 0.5h in a water bath kettle at 40 ℃, heating and stirring for 0.5h when the temperature of the water bath kettle is raised to 60 ℃, heating and stirring for 1h when the temperature of the water bath kettle is raised to 80 ℃, heating and stirring for more than 6h when the temperature of the water bath kettle is raised to 96 ℃, fully dissolving PVA particles, standing for 0.5h in a water bath kettle at 80 ℃, removing bubbles, preserving heat, and preparing a polyvinyl alcohol aqueous solution with the mass fraction of 12.5%;
s2, preparing a chitosan solution: weighing 4g of chitosan powder with deacetylation degree of 85%, weighing 96g of acetic acid with mass fraction of 1%, adding the chitosan powder into an acetic acid aqueous solution at normal temperature, stirring, filtering out insoluble substances, preparing to obtain a chitosan solution with mass fraction of 2%, and storing at room temperature for later use;
s3, preparing a zwitterionic polyurethane aqueous solution: reacting N, N-dihydroxyethyl isonicotinite (BINA), Hexamethylene Diisocyanate (HDI) and a catalyst in an organic solvent at 80 ℃ for 3-5 hours to synthesize shape memory polyurethane, then adding 1, 3-propane sultone (1,3-PS) to perform ring-opening reaction at 50 ℃ for more than 6 hours to obtain a mixed solution of zwitterionic polyurethane and the organic solvent, pouring the solution into a polytetrafluoroethylene disc, drying for 24 hours in an air-blast drying oven at 80 ℃, removing the organic solvent to obtain the zwitterionic polyurethane, finally dissolving part of the zwitterionic polyurethane in water, and preparing to obtain a zwitterionic polyurethane aqueous solution with the mass fraction of 10 wt%. Wherein the organic solvent is N, N-dimethylformamide, and the catalyst is dibutyltin dilaurate catalyst.
S4, preparation of the composite hydrogel: taking 5g of polyvinyl alcohol aqueous solution prepared in S1, 15g of chitosan solution prepared in S2 and 1g of zwitterionic polyurethane aqueous solution prepared in S3, uniformly mixing the polyvinyl alcohol aqueous solution, the chitosan solution and the zwitterionic polyurethane aqueous solution, performing ultrasonic treatment for 15 minutes to remove air bubbles in the solution to obtain a mixed solution, pouring the mixed solution into a mold, putting the mold into a refrigerator, freezing for 5 hours at-30 ℃, taking out the mold, standing for thawing for 2 hours at room temperature, and repeating the freezing-thawing operation for 3 times to obtain the composite hydrogel.
S5, freeze drying: and (3) placing the composite hydrogel obtained in the step (S4) into a freeze dryer with a cold trap temperature stabilized at-55 ℃ for pre-cooling, placing the pre-cooled aerogel into an iron disc of the freeze dryer after 2 hours, starting a vacuum pump to pump until the pressure is less than 5Pa, and freeze-drying for 24 hours to obtain the ZCPA-25 self-healing aerogel.
The aerogel obtained by the method can self-heal a heavy object which is 5000 times of the self weight in 60s, the mechanical strength under 70% compressive strain is 0.75MPa, the gaps are uniform, and the heat conductivity coefficient is 0.053W/mk. The microstructure of the aerogel is shown in figure 3.
Example 4
The embodiment relates to a self-healing aerogel, which is prepared by the following steps:
s1, preparing a polyvinyl alcohol aqueous solution: weighing 18.25g of polyvinyl alcohol, adding 131.25g of deionized water, heating and stirring for 0.5h in a water bath kettle at 40 ℃, heating and stirring for 0.5h when the temperature of the water bath kettle is raised to 60 ℃, heating and stirring for 1h when the temperature of the water bath kettle is raised to 80 ℃, heating and stirring for more than 6h when the temperature of the water bath kettle is raised to 96 ℃, fully dissolving PVA particles, standing for 0.5h in a water bath kettle at 80 ℃, removing bubbles, preserving heat, and preparing a polyvinyl alcohol aqueous solution with the mass fraction of 12.5%;
s2, preparing a chitosan solution: weighing 4g of chitosan powder with deacetylation degree of 85%, weighing 96g of acetic acid with mass fraction of 1%, adding the chitosan powder into an acetic acid aqueous solution at normal temperature, stirring, filtering out insoluble substances, preparing to obtain a chitosan solution with mass fraction of 2%, and storing at room temperature for later use;
s3, preparing a zwitterionic polyurethane aqueous solution: reacting N, N-dihydroxyethyl isonicotinite (BINA), Hexamethylene Diisocyanate (HDI) and a catalyst in an organic solvent at 80 ℃ for 3-5 hours to synthesize shape memory polyurethane, then adding 1, 3-propane sultone (1,3-PS) to perform ring-opening reaction at 50 ℃ for more than 6 hours to obtain a mixed solution of zwitterionic polyurethane and the organic solvent, pouring the solution into a polytetrafluoroethylene disc, drying for 24 hours in an air-blast drying oven at 80 ℃, removing the organic solvent to obtain the zwitterionic polyurethane, finally dissolving part of the zwitterionic polyurethane in water, and preparing to obtain a zwitterionic polyurethane aqueous solution with the mass fraction of 10 wt%. Wherein the organic solvent is N, N-dimethylformamide, and the catalyst is dibutyltin dilaurate catalyst.
S4, preparation of the composite hydrogel: taking 6g of polyvinyl alcohol aqueous solution prepared in S1, 14g of chitosan solution prepared in S2 and 1g of zwitterionic polyurethane aqueous solution prepared in S3, uniformly mixing the polyvinyl alcohol aqueous solution, the chitosan solution and the zwitterionic polyurethane aqueous solution, performing ultrasonic treatment for 15 minutes to remove air bubbles in the solution to obtain a mixed solution, pouring the mixed solution into a mold, putting the mold into a refrigerator, freezing the mold at-30 ℃ for 5 hours, taking the mold out, standing the mold for thawing at room temperature for 2 hours, and repeating the freezing-thawing operation for 3 times to obtain the composite hydrogel.
S5, freeze drying: and (3) placing the composite hydrogel obtained in the step (S4) into a freeze dryer with a cold trap temperature stabilized at-55 ℃ for pre-cooling, placing the pre-cooled aerogel into an iron disc of the freeze dryer after 2 hours, starting a vacuum pump to pump until the pressure is less than 5Pa, and freeze-drying for 24 hours to obtain the ZCPA-30 self-healing aerogel.
The aerogel obtained by the method can self-heal a heavy object which is 5000 times of the self weight in 60s, the mechanical strength under 70% compressive strain is 1.3MPa, the gaps are uniform, and the heat conductivity coefficient is 0.068W/mk. The microstructure of the aerogel is shown in figure 4.
Test example 1:
the thermal insulation effect of the self-healing aerogel provided in embodiments 1 and 2 is detected by using an IKA RCT Basic stirring thermal platform, the thermal platform is first heated to 120 ℃, then the self-healing aerogel provided in embodiments 1 and 2 is placed on the thermal platform, after heating for 5min, the self-healing aerogel is photographed by using a FLUKE Ti110 infrared thermal imager, and the detection result is as shown in fig. 5, wherein the left side of fig. 5 is a thermal insulation effect diagram of the self-healing aerogel provided in embodiment 1, and the right side of fig. 5 is a thermal insulation effect diagram of the self-healing aerogel provided in embodiment 2, and according to detection, the thermal insulation effect of the self-healing aerogel provided in embodiment 1 is better than that of embodiment 2.
Test example 2:
the mechanical properties of the self-healing aerogels provided in examples 1 to 4 were tested according to GB/T1041-1992 compression test gel, and the test results are shown in fig. 6, where the mechanical strength of example 1 under 70% compressive strain is 0.46 MPa; the mechanical strength of example 2 at 70% compressive strain was 0.6MPa, and the mechanical strength of example 3 at 70% compressive strain was 0.75 MPa; example 4 had a mechanical strength of 1.3MPa at 70% compressive strain.
Test example 3:
the self-healing effect of the self-healing aerogel provided in example 2 was examined using a thermal field emission scanning electron microscope (model NGB4-DXS-10AC, Hitachi, Japan).
Firstly, a gap (a part shown by a black frame line in the figure) is formed in the self-healing aerogel provided by the embodiment 2, then a small amount of water is uniformly sprayed at the gap, the healing condition of the self-healing aerogel is observed, the detection result is shown in fig. 7, and the self-healing aerogel provided by the embodiment 2 has an obvious healing effect as seen from the microstructure.
Test example 4:
the mechanical properties of the self-healing aerogel provided in example 2 before and after self-healing were tested according to the tensile property test of GB 13022-; the self-healed sample fractured at a strain of 340%, and the stress at this time was 0.36 MPa.
Test example 5:
the heat insulation performance of the self-healing aerogel provided in the embodiments 1 to 4 is detected according to a GB 3399-82 plastic heat conductivity coefficient test method, and the detection result shows that the heat conductivity coefficient of the embodiment 1 is 0.046W/mk; the thermal conductivity of example 2 was 0.049W/mk; the thermal conductivity of example 3 was 0.053W/mk; the thermal conductivity of example 4 was 0.068W/mk.
It should be understood that the above examples are only for clarity of illustration and are not intended to limit the embodiments. Other variations and modifications will be apparent to persons skilled in the art in light of the above description. And are neither required nor exhaustive of all embodiments. And obvious variations or modifications therefrom are within the scope of the invention.
Claims (10)
1. The self-healing aerogel is characterized by being prepared according to the following steps:
mixing a biomass polysaccharide solution with the mass fraction of less than or equal to 5 wt% and a polyvinyl alcohol aqueous solution with the mass fraction of 5 wt% -20 wt% according to the weight ratio of 100: (15-35) preparing a composite hydrogel material by mixing according to the mass ratio, and then freezing and drying the composite hydrogel material to obtain the self-healing aerogel;
wherein the polyvinyl alcohol has an average degree of polymerization of 1000-2000.
2. A self-healing aerogel according to claim 1, wherein the biomass polysaccharide is at least one of chitosan and sodium alginate.
3. A self-healing aerogel according to claim 2, wherein the biomass polysaccharide solution is a chitosan solution prepared from chitosan powder with a deacetylation degree of 65% -90% and acetic acid solution with a mass fraction of 1% -5%.
4. The self-healing aerogel according to any one of claims 1 to 3, wherein the raw materials for preparing the composite hydrogel material further comprise a zwitterionic polyurethane aqueous solution with a mass fraction of 5 wt% to 20 wt%.
5. A self-healing aerogel according to any one of claims 1 to 4, wherein the biomass polysaccharide solution, the zwitterionic polyurethane aqueous solution and the polyvinyl alcohol aqueous solution are added in a mass ratio of 100: (1-10): (15-35).
6. A self-healing aerogel according to claim 4 or 5, wherein the aqueous zwitterionic polyurethane solution is prepared by mixing N, N-dihydroxyethyl isonicotinite, hexamethylene diisocyanate and 1, 3-propane sultone.
7. The self-healing aerogel according to claim 6, wherein the preparation of the aqueous zwitterionic polyurethane solution comprises the following steps:
reacting N, N-dihydroxyethyl isonicotinite, hexamethylene diisocyanate and a catalyst in an organic solvent at the temperature of 80 ℃ for 3-5 hours to synthesize shape memory polyurethane, adding 1, 3-propane sultone, carrying out ring opening reaction at the temperature of 50 ℃ for more than 6 hours to obtain a mixed solution of zwitterionic polyurethane and the organic solvent, removing the organic solvent to obtain zwitterionic polyurethane, and dissolving the zwitterionic polyurethane in water to obtain a zwitterionic polyurethane aqueous solution.
8. A self-healing aerogel according to claim 7, wherein the organic solvent is at least one of N, N-dimethylformamide, N-dimethylacetamide, tetrahydrofuran, dimethylsulfoxide, and/or the catalyst is dibutyltin dilaurate catalyst.
9. A self-healing aerogel according to any of claims 1 to 8, wherein the preparation of the composite hydrogel material comprises the following steps:
uniformly mixing the raw materials of the composite hydrogel material, and ultrasonically mixing for 10-30 minutes to remove bubbles to obtain a mixed solution;
freezing the mixed solution at-50-0 ℃ for 10-20 h;
unfreezing the frozen mixed solution at room temperature for 1-5 h;
repeating the freezing-unfreezing operation for 1-5 times to obtain the composite hydrogel material.
10. A self-healing aerogel according to any of claims 1 to 9, wherein the step of freeze-drying the composite hydrogel material to obtain the self-healing aerogel comprises the step of placing the composite hydrogel material in a vacuum environment with a pressure of less than 5Pa and freeze-drying the composite hydrogel material at-55 ℃ for 12 to 48 hours.
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| CN115073913A (en) * | 2022-07-19 | 2022-09-20 | 张健明 | Biodegradable polyurethane-based material and preparation method thereof |
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