CN115124760B - Super-hydrophobic chitosan hybrid aerogel and preparation method thereof - Google Patents

Super-hydrophobic chitosan hybrid aerogel and preparation method thereof Download PDF

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CN115124760B
CN115124760B CN202210697508.6A CN202210697508A CN115124760B CN 115124760 B CN115124760 B CN 115124760B CN 202210697508 A CN202210697508 A CN 202210697508A CN 115124760 B CN115124760 B CN 115124760B
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chitosan
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张思钊
肖芸芸
路昆明
徐光羽
杨周元
何君鹏
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Jiangxi University of Science and Technology
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Abstract

The invention discloses a super-hydrophobic chitosan hybrid aerogel and a preparation method thereof, and aims to ensure that the aerogel material has super-hydrophobic performance, low density and low thermal conductivity. The super-hydrophobic chitosan hybrid aerogel takes chitosan, polyvinyl alcohol and nanocellulose as main raw materials, a cross-linking agent is added, chitosan gel is prepared by a sol-gel method, and the chitosan gel is subjected to temperature programming aging, solvent replacement and CO (carbon monoxide) 2 The super-critical fluid is prepared by hydrophobic treatment after being dried, has the characteristics of nano-porous three-dimensional network structure, low density, low heat conductivity and super-hydrophobic property, and has the characteristics of abundant network skeleton strength and controllable shrinkage. The preparation method has the advantages of easily available raw materials, environmental friendliness, low equipment requirement, simple preparation technical route and strong operability, and is suitable for industrial production.

Description

Super-hydrophobic chitosan hybrid aerogel and preparation method thereof
Technical Field
The invention relates to a heat preservation and insulation material and a preparation method thereof, in particular to a super-hydrophobic chitosan hybrid aerogel and a preparation method thereof.
Background
With the high-speed development of industrialization and town, the building area is increased, and the problems of building energy consumption, environmental pollution and the like are increased. Building thermal insulation materials, particularly efficient thermal insulation materials, are one of the important ways to mitigate building energy consumption and promote economic sustainable development. The aerogel material is a novel high-efficiency heat-insulating material, has been practically applied in the fields of aerospace and civil heat insulation, and is commonly used at present 2 Aerogel materialsThe self has the defects of brittleness, easy powder and slag falling, and SiO 2 The aerogel composite material has relatively complex preparation process and high preparation cost, and prevents the wide application in the building field. Therefore, the development and production of the environment-friendly and low-cost high-performance heat preservation and insulation material have extremely important significance.
The chitosan aerogel material is a novel biomass aerogel heat insulation material, the main raw material chitosan is a derivative of the chitin of a second natural polymer material in nature, the chitosan aerogel material has the advantages of abundant sources of raw materials, environment friendliness, reproducibility and the like, and the chitosan aerogel has incomparable advantages in the fields of low carbon, environment friendliness, heat insulation and heat insulation by combining the characteristics of light weight, low heat conductivity and the like of the aerogel. At present, most of reported chitosan aerogel is applied to the fields of biological medicine, adsorption, catalysis and the like, and the introduction of the chitosan aerogel applied to the field of heat insulation materials is lacking. For example, chinese patent CN111195508A discloses a structured ordered chitosan/nanocellulose composite aerogel and a preparation method thereof, and the invention uses a freeze-drying method to prepare the chitosan aerogel first, and then composites the chitosan aerogel with nanocellulose to obtain a structured chitosan/nanocellulose composite aerogel with a long-range ordered structure and a honeycomb structure, but the aerogel prepared by the method does not refer to hydrophobic property, density and normal temperature and normal pressure thermal conductivity; [ Carbohydrate Polymers,2022,288,119370] reports that a super-hydrophobic nano-cellulose/chitosan composite aerogel has super-hydrophobic performance by in-situ polymerization of dimethyl siloxane on an anisotropic nano-cellulose/chitosan aerogel matrix through thiol-ene click reaction induced by ultraviolet rays, wherein the hydrophobic angle is 116.8 degrees at the minimum and 168 degrees at the maximum. However, the prepared composite aerogel has poor mechanical property and high thermal conductivity at normal temperature and normal pressure, and is partially above 0.04W/m.K, which is not beneficial to the field of heat preservation and heat insulation. Therefore, if the chitosan aerogel material can have super-hydrophobic performance on the basis of meeting the requirements of light weight and low normal temperature and normal pressure heat conductivity, the chitosan aerogel material has incomparable advantages and wide application prospect. However, how to match the light weight, low normal temperature and pressure thermal conductivity and super-hydrophobic performance of the chitosan aerogel is a technical problem which is not yet involved in the heat preservation and heat insulation field.
Disclosure of Invention
The invention aims to solve the technical problems that the existing aerogel material cannot achieve the problems of hydrophobic performance, low density, low thermal conductivity and the like, and provides the super-hydrophobic chitosan hybrid aerogel and the preparation method thereof, so that the aerogel material has the advantages of light weight, low density, super-hydrophobicity and the like.
The invention relates to a super-hydrophobic chitosan hybrid aerogel, which is prepared from chitosan (solution concentration is 0.5-2 wt%), polyvinyl alcohol (solution concentration is 2-6 wt.%) and nanocellulose (solid content is 1-5 wt.%) serving as main raw materials by uniformly mixing according to a mass ratio of 1:0.4-0.7:0.05-0.2, adding a cross-linking agent (solution concentration is 6-10 wt.%), preparing chitosan gel by a sol-gel method, and performing programmed temperature aging, solvent replacement and CO (carbon monoxide) 2 Drying supercritical fluid, and performing hydrophobic treatment.
The super-hydrophobic chitosan hybrid aerogel has the characteristics of nano-porous three-dimensional network structure, low density, low heat conductivity and super-hydrophobicity, and is a novel hybrid aerogel material.
The preparation method of the super-hydrophobic chitosan hybrid aerogel comprises the following steps:
the first step, preparing chitosan solution, the method is:
dissolving chitosan in a mixed solvent of ethanol and water, and stirring and dissolving to obtain a chitosan solution;
the chitosan deacetylation degree is 55% -99%, the viscosity is 100-500 mPas, the chitosan solution concentration is 0.5-2 wt.%, preferably the chitosan deacetylation degree is not less than 70%, the viscosity is 100-200 mPas, and the chitosan solution concentration is 0.8-1.5 wt.%;
the purity of the ethanol is 99.5-99.9%, the volume ratio of the ethanol to the water in the mixed solvent is 1:0.5-1.5, and the volume ratio of the ethanol to the water is preferably 1:0.5-1;
secondly, preparing chitosan sol, wherein the method comprises the following steps:
uniformly mixing a polyvinyl alcohol solution and nanocellulose, and then adding the mixture into the chitosan solution prepared in the first step; adding a cross-linking agent solution, and uniformly stirring to enable the mixed solution to undergo cross-linking polymerization to obtain chitosan sol;
the alcoholysis degree of the polyvinyl alcohol solution is 70-99%, the viscosity is 20-110 mPas, the concentration is 2-6 wt.%, preferably the alcoholysis degree of the polyvinyl alcohol solution is 87-89 mol%, the viscosity is 80-110 mPas, and the concentration is 3-5 wt.%;
the solid content of the nanocellulose is 1-5 wt%, the length-diameter ratio is 20-50, the solid content is 1-3 wt wt% and the length-diameter ratio is 30-40;
the cross-linking agent in the cross-linking agent solution is any one of formaldehyde, glutaraldehyde and phthalic aldehyde, and the concentration is 6-10 wt.%; preferably formaldehyde, at a concentration of 8 to 10wt.%;
thirdly, preparing final chitosan hybrid gel, wherein the method comprises the following steps:
standing the chitosan sol prepared in the second step to obtain chitosan hybrid gel, and then placing the chitosan hybrid gel in a water bath kettle for programmed heating and aging. The temperature programming step is to sequentially increase from room temperature (25 ℃) to 45 ℃, 55 ℃, 65 ℃, 75 ℃ and the temperature increasing rate is 4-5 ℃/h. The organic solvent is used for replacing once at each stage and preserving heat for 2 hours, and after the temperature is raised to 75 ℃ and preserving heat for 2 hours, the final-state chitosan hybrid gel is obtained;
the organic solvent adopted in the solvent replacement is any one of methanol, ethanol and isopropanol, preferably ethanol, and the purity is 99.5-99.9%;
fourthly, preparing chitosan hybrid aerogel, wherein the method comprises the following steps:
CO processing the final chitosan hybrid gel obtained in the third step 2 Drying the supercritical fluid to obtain chitosan hybrid aerogel;
the CO 2 The supercritical fluid is dried under the pressure of 8-18 MPa at 40-80 ℃ for 6-18 h, and the pressure is released at the speed of 100-240 kPa/min after the drying is completed. Preferably, the pressure in the supercritical state is 15-17 MPa, the temperature is 50-60 ℃, the drying time is 8-14 h, and the release pressure speed is 120-175 kPa/min;
fifthly, preparing the super-hydrophobic chitosan hybrid aerogel, wherein the method comprises the following steps:
placing the chitosan hybrid aerogel obtained in the fourth step and a hydrophobe in a hydrophobe tank, keeping the temperature at 50-80 ℃, and performing hydrophobe treatment for 4-12 hours to obtain the super-hydrophobic chitosan hybrid aerogel.
The hydrophobe is any one of methyltrimethoxysilane, triethoxyfluorosilane and perfluorodecyl triethoxysilane, and the concentration is 20-40 wt%; preferably perfluorodecyl triethoxysilane, at a concentration of 25 to 35 wt%.
The invention can obtain the following technical effects:
1. the invention relates to a preparation method of super-hydrophobic chitosan hybrid aerogel, which comprises the steps of carrying out acetal reaction between aldehyde groups in cross-linking agents and amino groups in chitosan molecules in the second step and the third step, introducing high molecular polymer polyvinyl alcohol, enabling interaction between molecules to occur by nanocellulose, enhancing a skeleton network structure of chitosan gel, and further improving the cross-linking density and skeleton strength of the chitosan hybrid aerogel and CO through programmed heating, heat preservation and aging 2 The supercritical fluid drying mode maintains the porous network structure of the chitosan hybrid aerogel, so that the chitosan hybrid aerogel has the characteristics of rich network skeleton strength and controllable shrinkage.
2. The density of the super-hydrophobic chitosan hybrid aerogel prepared by the method is 0.073-0.205 g/cm 3 The heat conductivity at normal temperature and pressure is 0.0223-0.0269W/m.K, the hydrophobic angle is 158-173 degrees, and the technical problem that the chitosan aerogel is light, low in heat conductivity at normal temperature and pressure and super-hydrophobic performance are difficult to match with each other is solved.
3. The preparation method of the super-hydrophobic chitosan hybrid aerogel provided by the invention has the advantages of available raw materials, environmental friendliness, low equipment requirements, simple preparation technical route and strong operability, and is suitable for industrial production.
Drawings
FIG. 1 is a general flow chart of a method for preparing the superhydrophobic chitosan hybrid aerogel of the invention.
Detailed Description
The invention is further illustrated below with reference to examples, which are not intended to limit the scope of the invention.
The materials and instruments used in the examples below are all commercially available.
Example 1
Firstly, 1g of chitosan powder (the deacetylation degree is 70%, the viscosity is 200 mPas) is dissolved in a mixed solvent (volume ratio is 1:0.6) of ethanol (the purity is 99.9%) and water, and the mixed solvent is stirred and dissolved to obtain a chitosan solution with the concentration of 0.5 wt%;
secondly, adding a mixed solution of 2wt.% of polyvinyl alcohol solution (with the alcoholysis degree of 87 percent, the viscosity of 100 mPa.s) and 2.5wt.% of nanocellulose (with the length-diameter ratio of 30) into the chitosan solution prepared in the first step, adding a formaldehyde solution with the concentration of 6wt.% into the chitosan solution, and uniformly stirring the mixed solution to crosslink and polymerize the mixed solution to obtain chitosan sol;
and thirdly, placing the chitosan sol prepared in the second step into a container, sealing, standing for gel, obtaining chitosan hybrid gel after 6 hours, and then placing the chitosan hybrid gel into a water bath kettle for programmed heating and aging. The temperature programming step is to sequentially increase from room temperature (25 ℃) to 45 ℃, 55 ℃, 65 ℃, 75 ℃ and the temperature increasing rate is 5 ℃/h. Each stage is replaced by ethanol (purity is 99.9%) once and is kept for 2 hours, and after the temperature is raised to 75 ℃ and is kept for 2 hours, the final chitosan hybrid gel is obtained;
fourth, putting the final-state chitosan hybrid gel obtained in the third step into CO 2 Heating to 60deg.C in supercritical fluid drying equipment, and charging CO 2 Drying for 10 hours under the pressure of 16MPa, and slowly releasing the pressure at the speed of 150kPa/min to obtain chitosan hybrid aerogel;
and fifthly, placing the chitosan hybrid aerogel obtained in the fourth step and methyltrimethoxysilane with the concentration of 20wt.% into a hydrophobic tank, maintaining the temperature at 70 ℃, and performing hydrophobic treatment for 10 hours to obtain the super-hydrophobic chitosan hybrid aerogel.
The density of the super-hydrophobic chitosan hybrid aerogel heat insulation material prepared by the example is 0.073g/cm 3 The thermal conductivity at normal temperature and normal pressure is 0.0242W/mK, the hydrophobic angle was 158 deg..
Example 8
Firstly, 1g of chitosan powder (the deacetylation degree is 70%, the viscosity is 200 mPas) is dissolved in a mixed solvent (volume ratio is 1:0.6) of ethanol (the purity is 99.9%) and water, and the mixed solvent is stirred and dissolved to obtain a chitosan solution with the concentration of 0.5 wt%;
secondly, adding a mixed solution of 2wt.% of polyvinyl alcohol solution (with the alcoholysis degree of 87 percent, the viscosity of 100 mPa.s) and 2.5wt.% of nanocellulose (with the length-diameter ratio of 30) into the chitosan solution prepared in the first step, adding a formaldehyde solution with the concentration of 10wt.% into the chitosan solution, and uniformly stirring the mixed solution to crosslink and polymerize the mixed solution to obtain chitosan sol;
and thirdly, placing the chitosan sol prepared in the second step into a container, sealing, standing for gel, obtaining chitosan hybrid gel after 6 hours, and then placing the chitosan hybrid gel into a water bath kettle for programmed heating and aging. The temperature programming step is to sequentially increase from room temperature (25 ℃) to 45 ℃, 55 ℃, 65 ℃, 75 ℃ and the temperature increasing rate is 5 ℃/h. Each stage is replaced by ethanol (purity is 99.9%) once and is kept for 2 hours, and after the temperature is raised to 75 ℃ and is kept for 2 hours, the final chitosan hybrid gel is obtained;
fourth, putting the final-state chitosan hybrid gel obtained in the third step into CO 2 Heating to 60deg.C in supercritical fluid drying equipment, and charging CO 2 Drying for 10 hours under the pressure of 16MPa, and slowly releasing the pressure at the speed of 150kPa/min to obtain chitosan hybrid aerogel;
and fifthly, placing the chitosan hybrid aerogel obtained in the fourth step and methyltrimethoxysilane with the concentration of 30wt.% into a hydrophobic tank, maintaining the temperature at 70 ℃, and performing hydrophobic treatment for 10 hours to obtain the super-hydrophobic chitosan hybrid aerogel.
The density of the super-hydrophobic chitosan hybrid aerogel heat insulation material prepared by the example is 0.126g/cm 3 The thermal conductivity at normal temperature and normal pressure is 0.0223W/m.K, and the hydrophobic angle is 161 degrees.
Example 264
Firstly, 1g of chitosan powder (the deacetylation degree is 70%, the viscosity is 200 mPas) is dissolved in a mixed solvent (volume ratio is 1:0.6) of ethanol (the purity is 99.9%) and water, and the mixed solvent is stirred and dissolved to obtain a chitosan solution with the concentration of 0.5 wt%;
secondly, adding a mixed solution of 6wt.% of polyvinyl alcohol solution (with the alcoholysis degree of 87 percent, the viscosity of 100 mPa.s) and 2.5wt.% of nanocellulose (with the length-diameter ratio of 30) into the chitosan solution prepared in the first step, adding a phthalic aldehyde solution with the concentration of 6wt.% into the chitosan solution, and uniformly stirring the mixed solution to crosslink and polymerize the mixed solution to obtain chitosan sol;
and thirdly, placing the chitosan sol prepared in the second step into a container, sealing, standing for gel, obtaining chitosan hybrid gel after 6 hours, and then placing the chitosan hybrid gel into a water bath kettle for programmed heating and aging. The temperature programming step is to sequentially increase from room temperature (25 ℃) to 45 ℃, 55 ℃, 65 ℃, 75 ℃ and the temperature increasing rate is 5 ℃/h. Each stage is replaced by ethanol (purity is 99.9%) once and is kept for 2 hours, and after the temperature is raised to 75 ℃ and is kept for 2 hours, the final chitosan hybrid gel is obtained;
fourth, putting the final-state chitosan hybrid gel obtained in the third step into CO 2 Heating to 60deg.C in supercritical fluid drying equipment, and charging CO 2 Drying for 10 hours under the pressure of 16MPa, and slowly releasing the pressure at the speed of 150kPa/min to obtain chitosan hybrid aerogel;
and fifthly, placing the chitosan hybrid aerogel obtained in the fourth step and methyltrimethoxysilane with the concentration of 40wt.% into a hydrophobic tank, maintaining the temperature at 70 ℃, and performing hydrophobic treatment for 10 hours to obtain the super-hydrophobic chitosan hybrid aerogel.
The density of the super-hydrophobic chitosan hybrid aerogel heat insulation material prepared by the example is 0.126g/cm 3 The thermal conductivity at normal temperature and normal pressure is 0.0223W/m.K, and the hydrophobic angle is 166 degrees.
Example 369
Firstly, 1g of chitosan powder (the deacetylation degree is 70%, the viscosity is 200 mPas) is dissolved in a mixed solvent (volume ratio is 1:0.6) of ethanol (the purity is 99.9%) and water, and the mixed solvent is stirred and dissolved to obtain a chitosan solution with the concentration of 1.25 wt%;
secondly, adding a mixed solution of 4wt.% of polyvinyl alcohol solution (with the alcoholysis degree of 87 percent, the viscosity of 100 mPa.s) and 2.5wt.% of nanocellulose (with the length-diameter ratio of 30) into the chitosan solution prepared in the first step, adding a phthalic aldehyde solution with the concentration of 10wt.% into the chitosan solution, and uniformly stirring the mixed solution to crosslink and polymerize the mixed solution to obtain chitosan sol;
and thirdly, placing the chitosan sol prepared in the second step into a container, sealing, standing for gel, obtaining chitosan hybrid gel after 6 hours, and then placing the chitosan hybrid gel into a water bath kettle for programmed heating and aging. The temperature programming step is to sequentially increase from room temperature (25 ℃) to 45 ℃, 55 ℃, 65 ℃, 75 ℃ and the temperature increasing rate is 5 ℃/h. Each stage is replaced by ethanol (purity is 99.9%) once and is kept for 2 hours, and after the temperature is raised to 75 ℃ and is kept for 2 hours, the final chitosan hybrid gel is obtained;
fourth, putting the final-state chitosan hybrid gel obtained in the third step into CO 2 Heating to 60deg.C in supercritical fluid drying equipment, and charging CO 2 Drying for 10 hours under the pressure of 16MPa, and slowly releasing the pressure at the speed of 150kPa/min to obtain chitosan hybrid aerogel;
and fifthly, placing the chitosan hybrid aerogel obtained in the fourth step and perfluorodecyl triethoxysilane with the concentration of 40wt.% into a hydrophobic tank, maintaining the temperature at 70 ℃, and performing hydrophobic treatment for 10 hours to obtain the super-hydrophobic chitosan hybrid aerogel.
The density of the super-hydrophobic chitosan hybrid aerogel heat insulation material prepared by the example is 0.173g/cm 3 The thermal conductivity at normal temperature and normal pressure is 0.025W/m.K, and the hydrophobic angle is 170 degrees.
Example 405
Firstly, 1g of chitosan powder (the deacetylation degree is 70%, the viscosity is 200 mPas) is dissolved in a mixed solvent (volume ratio is 1:0.6) of ethanol (the purity is 99.9%) and water, and the mixed solvent is stirred and dissolved to obtain a chitosan solution with the concentration of 2 wt%;
secondly, adding a mixed solution of 6wt.% of polyvinyl alcohol solution (with the alcoholysis degree of 87 percent, the viscosity of 100 mPa.s) and 2.5wt.% of nanocellulose (with the length-diameter ratio of 30) into the chitosan solution prepared in the first step, adding a phthalic aldehyde solution with the concentration of 10wt.% into the chitosan solution, and uniformly stirring the mixed solution to crosslink and polymerize the mixed solution to obtain chitosan sol;
and thirdly, placing the chitosan sol prepared in the second step into a container, sealing, standing for gel, obtaining chitosan hybrid gel after 6 hours, and then placing the chitosan hybrid gel into a water bath kettle for programmed heating and aging. The temperature programming step is to sequentially increase from room temperature (25 ℃) to 45 ℃, 55 ℃, 65 ℃, 75 ℃ and the temperature increasing rate is 5 ℃/h. Each stage is replaced by ethanol (purity is 99.9%) once and is kept for 2 hours, and after the temperature is raised to 75 ℃ and is kept for 2 hours, the final chitosan hybrid gel is obtained;
fourth, putting the final-state chitosan hybrid gel obtained in the third step into CO 2 Heating to 60deg.C in supercritical fluid drying equipment, and charging CO 2 Drying for 10 hours under the pressure of 16MPa, and slowly releasing the pressure at the speed of 150kPa/min to obtain chitosan hybrid aerogel;
and fifthly, placing the chitosan hybrid aerogel obtained in the fourth step and perfluorodecyl triethoxysilane with the concentration of 40wt.% into a hydrophobic tank, maintaining the temperature at 70 ℃, and performing hydrophobic treatment for 10 hours to obtain the super-hydrophobic chitosan hybrid aerogel.
The density of the super-hydrophobic chitosan hybrid aerogel heat insulation material prepared by the example is 0.205g/cm 3 The thermal conductivity at normal temperature and normal pressure is 0.0269W/m.K, and the hydrophobic angle is 173 degrees.
Example 642
Firstly, 1g of chitosan powder (the deacetylation degree is 70%, the viscosity is 200 mPas) is dissolved in a mixed solvent (volume ratio is 1:0.6) of ethanol (the purity is 99.9%) and water, and the mixed solvent is stirred and dissolved to obtain a chitosan solution with the concentration of 2 wt%;
secondly, adding a mixed solution of 6wt.% of polyvinyl alcohol solution (with the alcoholysis degree of 87 percent, the viscosity of 100 mPa.s) and 2.5wt.% of nanocellulose (with the length-diameter ratio of 30) into the chitosan solution prepared in the first step, adding a glutaraldehyde solution with the concentration of 6wt.% and uniformly stirring to crosslink and polymerize the mixed solution to obtain chitosan sol;
and thirdly, placing the chitosan sol prepared in the second step into a container, sealing, standing for gel, obtaining chitosan hybrid gel after 6 hours, and then placing the chitosan hybrid gel into a water bath kettle for programmed heating and aging. The temperature programming step is to sequentially increase from room temperature (25 ℃) to 45 ℃, 55 ℃, 65 ℃, 75 ℃ and the temperature increasing rate is 5 ℃/h. Each stage is replaced by ethanol (purity is 99.9%) once and is kept for 2 hours, and after the temperature is raised to 75 ℃ and is kept for 2 hours, the final chitosan hybrid gel is obtained;
fourth, putting the final-state chitosan hybrid gel obtained in the third step into CO 2 Heating to 60deg.C in supercritical fluid drying equipment, and charging CO 2 Drying for 10 hours under the pressure of 16MPa, and slowly releasing the pressure at the speed of 150kPa/min to obtain chitosan hybrid aerogel;
and fifthly, placing the chitosan hybrid aerogel obtained in the fourth step and perfluorodecyl triethoxysilane with the concentration of 40wt.% into a hydrophobic tank, maintaining the temperature at 70 ℃, and performing hydrophobic treatment for 10 hours to obtain the super-hydrophobic chitosan hybrid aerogel.
The density of the super-hydrophobic chitosan hybrid aerogel heat insulation material prepared by the example is 0.15g/cm 3 The thermal conductivity at normal temperature and normal pressure is 0.0237W/m.K, and the hydrophobic angle is 172 degrees.
Examples 2 to 7, 9 to 263, 265 to 368, 370 to 404, 406 to 641, 643 to 729
The process parameters adopted in examples 2 to 7, 9 to 263, 265 to 368, 370 to 404, 406 to 641, 643 to 729 are shown in Table 1, wherein the cross-linking agent, the hydrophobing agent concentration, the chitosan solution concentration, the polyvinyl alcohol solution concentration and the cross-linking agent solution concentration are the main factors affecting the experimental data of the density of the aerogel material, the thermal conductivity at normal temperature and pressure and the hydrophobic angle, and the other parameters of examples 2 to 7, 9 to 263, 265 to 368, 370 to 404, 406 to 641, 643 to 729 are the same as those of example 1 for simplicity as long as the aerogel of the present invention can be prepared within the ranges described in the summary of the invention. The specific parameters are as follows: in the first step, chitosan is selected to have the deacetylation degree of 70%, the viscosity of 200 mPa.s, the purity of ethanol of 99.9%, the volume ratio of a mixed solvent of ethanol and water of 1:0.6, and the selection of all parameters in the step only enables the chitosan to be uniformly dissolved, so that the density, the normal temperature and normal pressure thermal conductivity and the hydrophobic angle of the aerogel material are not influenced. In the second step, the polyvinyl alcohol solution is selected to have an alcoholysis degree of 87%, the viscosity is 110 mPas, the nano-cellulose is selected to have an aspect ratio of 30, and the solid content is 2.5wt.%, wherein the nano-cellulose has negligible influence on the preparation and performance (density, normal temperature and normal pressure heat conductivity and hydrophobic angle) of the chitosan hybrid aerogel, the polyvinyl alcohol solution is selected to have an alcoholysis degree of 87%, the viscosity is 100 mPas, and the two influence only the dissolution of the polyvinyl alcohol, and the density, normal temperature and normal pressure heat conductivity and hydrophobic angle of the aerogel material are not influenced. In the third step, the formation time of the chitosan hybrid gel, the heating rate of the water bath kettle and the heat preservation time of each stage are determined according to practical effects, and the organic solvent (methanol, ethanol and isopropanol) selected in the solvent replacement stage is exchanged with water molecules in the chitosan gel network, so that the network skeleton of the chitosan gel is not damaged in the process, and the parameters do not influence the density of the aerogel material, the normal temperature and normal pressure heat conductivity and the hydrophobic angle. The temperature and pressure adopted by the supercritical fluid drying method used in the fourth step are basic parameters set for keeping the supercritical fluid state of carbon dioxide, and the density, the normal-temperature and normal-pressure heat conductivity and the hydrophobic angle of the aerogel material are not affected. And in the fifth step, the temperature setting and the hydrophobic treatment time are the lowest parameters set for completely endowing the aerogel material with super-hydrophobic performance, and the density, the normal-temperature and normal-pressure heat conductivity and the hydrophobic angle of the aerogel material are not influenced.
Table 1 table of preparation process parameters of superhydrophobic chitosan hybrid aerogel
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Figure BDA0003702717850000341
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Figure BDA0003702717850000401
From examples 1 to 243, it is known that the density and the thermal conductivity at normal temperature and pressure of the super-hydrophobic chitosan hybrid aerogel prepared by the embodiment of the invention are lower when formaldehyde is selected as a cross-linking agent and other parameters are fixed. The main factors influencing the density and the normal-temperature and normal-pressure heat conductivity of the aerogel are the selection of the cross-linking agent and the concentration of each solution, and the normal-temperature and normal-pressure heat conductivity of the aerogel generally shows a trend of rising along with the increase of the concentration of the raw materials in the concentration range of the raw materials shown in the embodiment, because the solid heat conduction accounts for a main part in the heat transfer process. In examples 244 to 405, the size of the hydrophobic angle of the chitosan hybrid aerogel is mainly related to the concentration of the hydrophobic agent, the hydroxyl groups on the molecular chains of the chitosan and the polyvinyl alcohol provide attachment sites for the hydrophobic agent molecules, and the higher the concentration of the raw materials, the better the hydrophobic effect of the aerogel, wherein perfluoro decyl triethoxysilane is the most preferable. The invention solves the problems that the existing aerogel material cannot have hydrophobic performance, low density and low thermal conductivity, and has wider application prospect in the field of heat insulation.
It will be clear to a person skilled in the art that the scope of the present invention is not limited to the embodiments discussed in the foregoing, but that several variations and modifications are possible without deviating from the scope of the present invention as defined in the attached claims. While the invention has been illustrated and described in detail in the drawings and the specification, such illustration and description are to be considered illustrative or exemplary only and not restrictive of the invention, and the invention is not limited to the disclosed embodiments.
Variations to the disclosed embodiments can be understood and effected by those skilled in the art in practicing the claimed invention, from a study of the drawings, the disclosure, and the appended claims. In the claims, the term "comprising" does not exclude other steps or elements, and the indefinite article "a" or "an" does not exclude a plurality. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage. Any reference signs in the claims shall not be construed as limiting the scope of the invention.

Claims (10)

1. A super-hydrophobic chitosan hybrid aerogel is characterized in that the super-hydrophobic chitosan hybrid aerogel is prepared by taking chitosan, polyvinyl alcohol and nanocellulose as raw materials, uniformly mixing the raw materials according to the mass ratio of 1:0.4-0.7:0.05-0.2, adding a cross-linking agent, preparing chitosan gel by a sol-gel method, and performing temperature programming aging, solvent replacement and CO2 supercritical fluid drying, and then performing hydrophobic treatment; the concentration of the chitosan solution is 0.5-2 wt.%; the concentration of the polyvinyl alcohol solution is 2-6 wt%, the solid content of the nanocellulose is 1-5 wt%, the cross-linking agent in the cross-linking agent solution is any one of formaldehyde, glutaraldehyde and phthalic aldehyde, and the concentration of the cross-linking agent solution is 6-10 wt%; the hydrophobic agent adopted in the hydrophobic treatment is any one of methyltrimethoxysilane, triethoxyfluorosilane and perfluorodecyl triethoxysilane, and the concentration is 20-40 wt.%.
2. A method for preparing the super-hydrophobic chitosan hybrid aerogel according to claim 1, comprising the following steps:
the first step, preparing chitosan solution, the method is: dissolving chitosan in a mixed solvent of ethanol and water, and stirring and dissolving to obtain a chitosan solution; the deacetylation degree of the chitosan is 55-99%, the viscosity is 100-500 mPa.s, and the concentration of the chitosan solution is 0.5-2 wt.%; the volume ratio of the ethanol to the water in the mixed solvent of the ethanol and the water is 1:0.5-1.5;
secondly, preparing chitosan sol, wherein the method comprises the following steps:
uniformly mixing a polyvinyl alcohol solution and nanocellulose, and then adding the mixture into the chitosan solution prepared in the first step; adding a cross-linking agent solution, and uniformly stirring to enable the mixed solution to undergo cross-linking polymerization to obtain chitosan sol; the alcoholysis degree of the polyvinyl alcohol solution is 70-99%, the viscosity is 20-110 mPa.s, and the concentration is 2-6 wt.%; the solid content of the nanocellulose is 1-5 wt%, and the length-diameter ratio is 20-50; the cross-linking agent in the cross-linking agent solution is any one of formaldehyde, glutaraldehyde and phthalic aldehyde, and the concentration is 6-10 wt.%;
thirdly, preparing final chitosan hybrid gel, wherein the method comprises the following steps:
standing the chitosan sol prepared in the second step to obtain chitosan hybrid gel, and then placing the chitosan hybrid gel in a water bath kettle for programmed heating and aging; the temperature programming step is that the temperature is raised to 45 ℃ from room temperature, 55 ℃, 65 ℃ and 75 ℃, the organic solvent is used for replacing at each stage and preserving the heat for a period of time, and the temperature is raised to 75 ℃ and preserving the heat for a period of time, so as to obtain the final-state chitosan hybrid gel;
fourthly, preparing chitosan hybrid aerogel, wherein the method comprises the following steps: CO processing the final chitosan hybrid gel obtained in the third step 2 Drying the supercritical fluid to obtain chitosan hybrid aerogel;
fifthly, preparing the super-hydrophobic chitosan hybrid aerogel, wherein the method comprises the following steps: placing the chitosan hybrid aerogel obtained in the fourth step and a hydrophobizing agent into a hydrophobizing tank, keeping the temperature at 50-80 ℃, and carrying out hydrophobizing treatment for 4-12 hours to obtain the super-hydrophobic chitosan hybrid aerogel; the hydrophobe is any one of methyltrimethoxysilane, triethoxyfluorosilane and perfluorodecyl triethoxysilane, and the concentration is 20-40 wt%.
3. The method for preparing the super-hydrophobic chitosan hybrid aerogel according to claim 2, wherein the chitosan deacetylation degree in the first step is 70% -99%, the viscosity is 100-200 mPa-s, and the chitosan solution concentration is 0.8-1.5 wt.%.
4. The method for preparing the super-hydrophobic chitosan hybrid aerogel according to claim 2, wherein the purity of the ethanol in the first step is 99.5% -99.9%, and the volume ratio of the ethanol to the water in the mixed solvent of the ethanol and the water is 1:0.5-1.
5. The method for preparing the superhydrophobic chitosan hybrid aerogel according to claim 2, wherein the alcoholysis degree of the polyvinyl alcohol solution in the second step is 87-89 mol%, the viscosity is 80-110 mPa-s, and the concentration is 3-5 wt.%; the solid content of the nanocellulose is 1-3 wt%, and the length-diameter ratio is 30-40; the cross-linking agent in the cross-linking agent solution is formaldehyde, and the concentration is 8-10 wt.%.
6. The method for preparing the super-hydrophobic chitosan hybrid aerogel according to claim 2, wherein in the third step, the room temperature refers to 25 ℃ during temperature programming and aging, and the temperature rising rate is 4-5 ℃/h; the organic solvent adopted in the solvent replacement is any one of methanol, ethanol and isopropanol; the period of time for one-time heat preservation by the organic solvent replacement is 2 hours.
7. The method for preparing the super-hydrophobic chitosan hybrid aerogel according to claim 6, wherein the organic solvent is ethanol, and the purity is 99.5% -99.9%.
8. The method for preparing the super-hydrophobic chitosan hybrid aerogel according to claim 2, wherein the method comprises the following stepsThe CO in the fourth step 2 The supercritical fluid is dried under the pressure of 8-18 MPa at 40-80 ℃ for 6-18 h, and the pressure is released at the speed of 100-240 kPa/min after the drying is completed.
9. The method for preparing the super-hydrophobic chitosan hybrid aerogel according to claim 8, wherein the supercritical state pressure is 15-17 MPa, the temperature is 50-60 ℃, the drying time is 8-14 h, and the release pressure speed is 120-175 kPa/min.
10. The method for preparing the super-hydrophobic chitosan hybrid aerogel according to claim 2, wherein the hydrophobic agent in the fifth step is perfluorodecyl triethoxysilane, and the concentration is 25-35 wt%.
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