CN115418021B - Cellulose aerogel, preparation method and application thereof - Google Patents
Cellulose aerogel, preparation method and application thereof Download PDFInfo
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- CN115418021B CN115418021B CN202211239034.7A CN202211239034A CN115418021B CN 115418021 B CN115418021 B CN 115418021B CN 202211239034 A CN202211239034 A CN 202211239034A CN 115418021 B CN115418021 B CN 115418021B
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- 239000004964 aerogel Substances 0.000 title claims abstract description 99
- 229920002678 cellulose Polymers 0.000 title claims abstract description 95
- 239000001913 cellulose Substances 0.000 title claims abstract description 95
- 238000002360 preparation method Methods 0.000 title claims abstract description 21
- 239000011148 porous material Substances 0.000 claims abstract description 27
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims abstract description 19
- 238000000034 method Methods 0.000 claims abstract description 17
- 230000001681 protective effect Effects 0.000 claims abstract description 10
- 230000008569 process Effects 0.000 claims abstract description 8
- 239000006185 dispersion Substances 0.000 claims description 27
- 239000003795 chemical substances by application Substances 0.000 claims description 25
- 239000007788 liquid Substances 0.000 claims description 19
- 238000010438 heat treatment Methods 0.000 claims description 16
- 238000007710 freezing Methods 0.000 claims description 13
- 230000008014 freezing Effects 0.000 claims description 13
- 239000012520 frozen sample Substances 0.000 claims description 8
- 229920002749 Bacterial cellulose Polymers 0.000 claims description 7
- 239000005016 bacterial cellulose Substances 0.000 claims description 7
- 238000004108 freeze drying Methods 0.000 claims description 7
- 239000005014 poly(hydroxyalkanoate) Substances 0.000 claims description 7
- 229920000903 polyhydroxyalkanoate Polymers 0.000 claims description 7
- 238000002156 mixing Methods 0.000 claims description 5
- 239000000463 material Substances 0.000 abstract description 23
- 239000002245 particle Substances 0.000 abstract description 11
- CURLTUGMZLYLDI-UHFFFAOYSA-N Carbon dioxide Chemical compound O=C=O CURLTUGMZLYLDI-UHFFFAOYSA-N 0.000 abstract description 8
- 239000002994 raw material Substances 0.000 abstract description 8
- 229910002092 carbon dioxide Inorganic materials 0.000 abstract description 4
- 239000001569 carbon dioxide Substances 0.000 abstract description 4
- 238000004064 recycling Methods 0.000 abstract description 4
- 231100000252 nontoxic Toxicity 0.000 abstract description 3
- 230000003000 nontoxic effect Effects 0.000 abstract description 3
- 229920000642 polymer Polymers 0.000 abstract description 3
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 18
- 239000000523 sample Substances 0.000 description 14
- 230000000052 comparative effect Effects 0.000 description 12
- 239000002184 metal Substances 0.000 description 10
- 230000006835 compression Effects 0.000 description 9
- 238000007906 compression Methods 0.000 description 9
- 229910052757 nitrogen Inorganic materials 0.000 description 9
- 239000013618 particulate matter Substances 0.000 description 9
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 6
- 125000004122 cyclic group Chemical group 0.000 description 6
- 239000007789 gas Substances 0.000 description 5
- 239000002121 nanofiber Substances 0.000 description 5
- 238000001878 scanning electron micrograph Methods 0.000 description 5
- 238000000498 ball milling Methods 0.000 description 4
- 239000013078 crystal Substances 0.000 description 4
- 239000004744 fabric Substances 0.000 description 4
- -1 polydimethylsiloxane Polymers 0.000 description 4
- 239000000843 powder Substances 0.000 description 4
- 239000002028 Biomass Substances 0.000 description 3
- 230000001276 controlling effect Effects 0.000 description 3
- 238000001816 cooling Methods 0.000 description 3
- 238000000354 decomposition reaction Methods 0.000 description 3
- 238000007865 diluting Methods 0.000 description 3
- 239000004205 dimethyl polysiloxane Substances 0.000 description 3
- 238000001914 filtration Methods 0.000 description 3
- 229920000435 poly(dimethylsiloxane) Polymers 0.000 description 3
- 229910002027 silica gel Inorganic materials 0.000 description 3
- 239000000741 silica gel Substances 0.000 description 3
- 229910052814 silicon oxide Inorganic materials 0.000 description 3
- KXGFMDJXCMQABM-UHFFFAOYSA-N 2-methoxy-6-methylphenol Chemical compound [CH]OC1=CC=CC([CH])=C1O KXGFMDJXCMQABM-UHFFFAOYSA-N 0.000 description 2
- 229920002201 Oxidized cellulose Polymers 0.000 description 2
- 239000000919 ceramic Substances 0.000 description 2
- 239000000428 dust Substances 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- 230000004048 modification Effects 0.000 description 2
- 238000012986 modification Methods 0.000 description 2
- 229940107304 oxidized cellulose Drugs 0.000 description 2
- 239000005011 phenolic resin Substances 0.000 description 2
- 229920001568 phenolic resin Polymers 0.000 description 2
- 239000002984 plastic foam Substances 0.000 description 2
- 238000000746 purification Methods 0.000 description 2
- 238000011084 recovery Methods 0.000 description 2
- 239000000243 solution Substances 0.000 description 2
- 238000012360 testing method Methods 0.000 description 2
- 241000894006 Bacteria Species 0.000 description 1
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 1
- BLRPTPMANUNPDV-UHFFFAOYSA-N Silane Chemical compound [SiH4] BLRPTPMANUNPDV-UHFFFAOYSA-N 0.000 description 1
- 239000007864 aqueous solution Substances 0.000 description 1
- 238000005452 bending Methods 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
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- 229910052799 carbon Inorganic materials 0.000 description 1
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- 238000013329 compounding Methods 0.000 description 1
- 238000010276 construction Methods 0.000 description 1
- 230000007123 defense Effects 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 238000001035 drying Methods 0.000 description 1
- 238000005265 energy consumption Methods 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 230000007613 environmental effect Effects 0.000 description 1
- 239000003344 environmental pollutant Substances 0.000 description 1
- 238000002474 experimental method Methods 0.000 description 1
- 239000000835 fiber Substances 0.000 description 1
- 239000003365 glass fiber Substances 0.000 description 1
- 239000001257 hydrogen Substances 0.000 description 1
- 229910052739 hydrogen Inorganic materials 0.000 description 1
- 230000002209 hydrophobic effect Effects 0.000 description 1
- 125000002887 hydroxy group Chemical group [H]O* 0.000 description 1
- 230000002401 inhibitory effect Effects 0.000 description 1
- 238000004519 manufacturing process Methods 0.000 description 1
- 238000005259 measurement Methods 0.000 description 1
- VUZPPFZMUPKLLV-UHFFFAOYSA-N methane;hydrate Chemical compound C.O VUZPPFZMUPKLLV-UHFFFAOYSA-N 0.000 description 1
- 231100000719 pollutant Toxicity 0.000 description 1
- 239000004810 polytetrafluoroethylene Substances 0.000 description 1
- 229920001343 polytetrafluoroethylene Polymers 0.000 description 1
- 230000001105 regulatory effect Effects 0.000 description 1
- 229920005989 resin Polymers 0.000 description 1
- 239000011347 resin Substances 0.000 description 1
- 229910000077 silane Inorganic materials 0.000 description 1
- 150000004756 silanes Chemical class 0.000 description 1
- 239000007787 solid Substances 0.000 description 1
- 238000001179 sorption measurement Methods 0.000 description 1
- 241000894007 species Species 0.000 description 1
- 239000012798 spherical particle Substances 0.000 description 1
Classifications
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
- C08J9/00—Working-up of macromolecular substances to porous or cellular articles or materials; After-treatment thereof
- C08J9/26—Working-up of macromolecular substances to porous or cellular articles or materials; After-treatment thereof by elimination of a solid phase from a macromolecular composition or article, e.g. leaching out
-
- A—HUMAN NECESSITIES
- A41—WEARING APPAREL
- A41D—OUTERWEAR; PROTECTIVE GARMENTS; ACCESSORIES
- A41D13/00—Professional, industrial or sporting protective garments, e.g. surgeons' gowns or garments protecting against blows or punches
- A41D13/05—Professional, industrial or sporting protective garments, e.g. surgeons' gowns or garments protecting against blows or punches protecting only a particular body part
- A41D13/11—Protective face masks, e.g. for surgical use, or for use in foul atmospheres
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
- C08J9/00—Working-up of macromolecular substances to porous or cellular articles or materials; After-treatment thereof
- C08J9/28—Working-up of macromolecular substances to porous or cellular articles or materials; After-treatment thereof by elimination of a liquid phase from a macromolecular composition or article, e.g. drying of coagulum
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
- C08J2201/00—Foams characterised by the foaming process
- C08J2201/04—Foams characterised by the foaming process characterised by the elimination of a liquid or solid component, e.g. precipitation, leaching out, evaporation
- C08J2201/046—Elimination of a polymeric phase
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
- C08J2201/00—Foams characterised by the foaming process
- C08J2201/04—Foams characterised by the foaming process characterised by the elimination of a liquid or solid component, e.g. precipitation, leaching out, evaporation
- C08J2201/048—Elimination of a frozen liquid phase
- C08J2201/0484—Elimination of a frozen liquid phase the liquid phase being aqueous
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
- C08J2205/00—Foams characterised by their properties
- C08J2205/02—Foams characterised by their properties the finished foam itself being a gel or a gel being temporarily formed when processing the foamable composition
- C08J2205/026—Aerogel, i.e. a supercritically dried gel
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
- C08J2301/00—Characterised by the use of cellulose, modified cellulose or cellulose derivatives
- C08J2301/02—Cellulose; Modified cellulose
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- Chemical & Material Sciences (AREA)
- Health & Medical Sciences (AREA)
- Engineering & Computer Science (AREA)
- Polymers & Plastics (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Medicinal Chemistry (AREA)
- Materials Engineering (AREA)
- Organic Chemistry (AREA)
- General Health & Medical Sciences (AREA)
- Physical Education & Sports Medicine (AREA)
- Textile Engineering (AREA)
- Manufacture Of Porous Articles, And Recovery And Treatment Of Waste Products (AREA)
- Polysaccharides And Polysaccharide Derivatives (AREA)
Abstract
The invention provides a cellulose aerogel, a preparation method and application thereof. The cellulose aerogel is provided with oriented pore channels and micropores distributed on the surface of the pore walls of the oriented pore channels, and the oriented pore channels are longitudinally distributed in the cellulose aerogel. The preparation method of the cellulose aerogel is environment-friendly, the whole process does not involve petrochemical-based organic matters or polymers, only water and a small amount of carbon dioxide are discharged, and experimental raw materials are nontoxic and harmless, so that industrialization is facilitated. The prepared cellulose aerogel has excellent rebound resilience and can meet the requirement of large deformation such as folding, torsion and the like. Meanwhile, the obtained cellulose aerogel has excellent rebound resilience even at-196 ℃, so that the material can be used in extreme environments. In addition, the cellulose aerogel has excellent particle removal rate, can be used for preparing protective masks, and has excellent recycling performance.
Description
Technical Field
The invention relates to the technical field of aerogel preparation, in particular to cellulose aerogel, a preparation method and application thereof.
Background
Aerogel is a material widely used in engineering, including the fields of national defense and military industry, aerospace, transportation, biomedicine, construction engineering and the like. The brittleness of the traditional phenolic resin and the aerogel derived from the phenolic resin, silicon oxide or ceramic and the like is high, which affects the practical use, for example, the silicon oxide aerogel is usually prepared into aerogel felt by using powder and glass fiber. However, the cellulose nanofiber has a large length-diameter ratio, and the aerogel assembled by the cellulose nanofiber has better flexibility and generally has large-size deformability and very wide application prospect compared with the traditional fragile aerogel such as carbon, silicon oxide or ceramic. Cellulose surfaces are rich in hydroxyl groups that form strong hydrogen bonding networks when the fibers are in close proximity to each other, thereby inhibiting rebound after deformation of the cellulose aerogel. To solve this problem, a series of cellulose aerogels with rebound resilience have been prepared by compounding with other materials or hydrophobically modifying cellulose with petrochemical materials such as silanes. However, the introduction of such petrochemical feedstocks greatly compromises the advantage of cellulose as an environmentally friendly biomass degradable material.
Disclosure of Invention
In view of the above, the present invention is directed to a cellulose aerogel, a preparation method and an application thereof. The preparation method does not relate to petrochemical raw materials, does not discharge solid, liquid and gas pollutants, is environment-friendly, is simple to operate, is safe and reliable, and the obtained cellulose aerogel has oriented pore channels and micropores distributed on the surfaces of the oriented pore channel structures, has excellent rebound resilience, and can meet the requirements of large deformation such as folding, torsion and the like.
In order to achieve the purpose, the invention adopts the following technical scheme:
in a first aspect, the present invention provides a cellulose aerogel having oriented cells and micropores distributed on the surface of the walls of the oriented cells.
Preferably, the oriented channels are longitudinally distributed inside the cellulose aerogel.
Preferably, the diameter of the oriented channels is 45-60 μm.
Preferably, the pore diameter of the micropores is 0.5-2 μm.
In a second aspect, the present invention provides a method for preparing the cellulose aerogel, comprising the steps of:
(1) Mixing cellulose, a pore-forming agent and water to obtain a dispersion;
(2) Orientation freezing is carried out on the dispersion liquid, and then the frozen sample block is dried to obtain an intermediate;
(3) And performing heat treatment on the intermediate to obtain the cellulose aerogel.
Preferably, the ratio of the cellulose, the pore-forming agent and the water is (0.05-1) g (90-120) mL.
Preferably, the cellulose comprises bacterial cellulose and/or lignocellulose.
Preferably, the pore-forming agent comprises a polyhydroxyalkanoate.
Preferably, the orientation freezing process is cooled at a rate of 1-10 ℃/min until the dispersion agglomerates.
Preferably, the temperature of the freeze drying is-70 to-90 ℃, and the time of the freeze drying is 24-72 hours.
Preferably, the temperature of the heat treatment is 140-200 ℃, and the time of the heat treatment is 4-24 hours.
In a third aspect, the present invention provides a protective mask comprising the cellulose aerogel or the cellulose aerogel prepared according to the preparation method.
Compared with the prior art, the invention has the beneficial effects that:
(1) The preparation method provided by the invention is environment-friendly, the whole process does not involve the use of petrochemical-based organic matters or polymers, only water and a small amount of carbon dioxide are discharged, the used experimental raw materials are nontoxic and harmless, the experimental raw materials can be obtained in batches, the cost is low, and the obtained product can be completely degraded by biomass, so that the industrial large-scale application is facilitated;
(2) The cellulose aerogel material prepared by the preparation method provided by the invention has excellent rebound resilience, can meet the requirement of large deformation such as folding, torsion and the like, and greatly improves the structural stability of the product so as to be suitable for different working scenes. Meanwhile, the obtained cellulose aerogel has excellent rebound resilience even at-196 ℃, so that the material can be used in extreme environments, such as space deep space;
(3) The cellulose aerogel material prepared by the preparation method provided by the invention has oriented pore channels and micropores distributed on the surface of the oriented pore channel structure, has good adsorptivity, can be used for preparing protective masks, has a particle removal rate which is comparable to that of commercial masks, and has excellent recycling property.
Drawings
FIG. 1 is an SEM image of a pore-forming agent (polyhydroxyalkanoate);
FIG. 2 is a SEM image of a longitudinal section of the cellulose aerogel obtained in example 1;
FIG. 3 is an SEM image of a disordered cellulose aerogel obtained according to comparative example 1;
FIG. 4 is a graph comparing cyclic stress-strain curves of cellulose aerogels obtained in example 1 and comparative example 1;
FIG. 5 is a graphical representation of rebound after compression to 50% strain of the cellulose aerogels obtained in example 1 and comparative example 1;
FIG. 6 is a physical comparison of the cellulose aerogels obtained in example 1 and comparative example 1 after recovery after torsion;
FIG. 7 is a physical view showing recovery of the cellulose aerogel obtained in example 1 after folding;
FIG. 8 is a graphical representation of the resilience of the cellulose aerogel obtained in example 1 after 80% deformation under compression at-196 ℃;
FIG. 9 is a graph comparing cyclic stress-strain curves of the aerogel obtained in example 1 after 10, 100 and 10 ten thousand cycles of cyclic compression at 50% strain;
FIG. 10 is a graph comparing the efficiency of particulate filtration of aerogel obtained in example 1 with that of a commercial protective mask;
FIG. 11 is a graph showing the filtration performance and the piezoresistive cycle performance of the aerogel particles obtained in example 1.
Detailed Description
The technical solutions of the present invention will be clearly and completely described in conjunction with the embodiments of the present invention, and it is apparent that the described embodiments are only some embodiments of the present invention, but not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
The sources of all the raw materials involved in the present invention are not particularly limited, and they may be commercially available or prepared according to conventional preparation methods well known to those skilled in the art.
The invention provides a cellulose aerogel, which is provided with oriented pore channels and micropores distributed on the surface of the pore walls of the oriented pore channels, wherein the oriented pore channels are longitudinally distributed in the cellulose aerogel.
The cellulose aerogel is provided with multistage holes, and comprises primary oriented pore channels and micropores distributed on the surfaces of the pore walls of the oriented pore channels. In the present invention, the diameter of the oriented pore structure is preferably 45 to 60 μm, more preferably 45 to 55 μm; the pore diameter of the micropores is preferably 0.5 to 2. Mu.m, more preferably 0.5 to 1. Mu.m. The cellulose aerogel with the multistage holes has excellent rebound resilience, can meet the requirement of large deformation such as folding, torsion and the like, and greatly improves the structural stability of the product so as to be suitable for different working scenes. Meanwhile, the material has excellent adsorptivity and can be used as an excellent adsorption material.
The invention also provides a preparation method of the cellulose aerogel, which comprises the following steps:
(1) Mixing cellulose, a pore-forming agent and water to obtain a dispersion;
(2) Orientation freezing is carried out on the dispersion liquid, and then the frozen sample block is dried to obtain an intermediate;
(3) And performing heat treatment on the intermediate to obtain the cellulose aerogel.
According to the invention, cellulose, a pore-forming agent and water are first mixed to obtain a dispersion. The invention is not particularly limited in the order of addition, and preferably, cellulose is mixed with water to obtain a cellulose solution, and then a pore-forming agent is added to mix to obtain a dispersion. More preferably, the pore-forming agent is added and then ball-milled and mixed to obtain particles with smaller particle diameters, wherein the rotation speed of the ball-milling and mixing is preferably 100-300 r/min, more preferably 150-250 r/min, and the time of the ball-milling is preferably 12-36 h, more preferably 24-36 h. The cellulose may be non-oxidized cellulose or oxidized cellulose, preferably the cellulose species comprises bacterial cellulose and/or lignocellulose. The pore-forming agent preferably comprises polyhydroxyalkanoate which is produced by bacteria, the production energy consumption is low, and the decomposition product only comprises carbon dioxide and water, so that the pore-forming agent meets the requirements of environmental protection. In the present invention, the aqueous solution of cellulose is used as the main source of the cellulose aerogel, and the pore-forming agent is used for forming micropores in the cellulose aerogel, so that the cellulose, the pore-forming agent and water are regarded as a whole, and the ratio of the cellulose, the pore-forming agent and the water is (0.05-1) g, (90-120) mL, more preferably (0.1-0.5) g, (0.1-1) g, (90-110) mL.
After the dispersion was obtained, the dispersion was subjected to orientation freezing, and the frozen sample was dried to obtain an intermediate. The orientation freezing is a conventional technical means well known to those skilled in the art, specifically, a metal platform is immersed in a liquid nitrogen environment, a thermocouple is connected to the surface of the metal platform, the temperature of the surface of the metal platform is regulated and controlled by controlling the addition amount of liquid nitrogen, and the method can control the error of the surface temperature of the metal platform within 3 ℃. In the invention, the size and shape of the prepared honeycomb resin material are controlled by moulds with different sizes and shapes, and the material of the mould preferably comprises any one of silica gel, polydimethylsiloxane or polytetrafluoroethylene. More specifically, the invention preferably places the metal platform in a container, places a die, then pours the dispersion liquid, adds liquid nitrogen to control the surface of the metal platform to cool at a speed of 1-10 ℃/min until the dispersion liquid is agglomerated, and more preferably cools at a speed of 5-10 ℃/min, so as to obtain frozen sample blocks. In the process, water is gradually solidified along with the temperature gradient to form ice crystals, the ice crystals squeeze cellulose and pore-forming agents, and the process can take the ice crystals as an orientation template of colloidal particles to play a role of physical confinement.
And then drying the frozen sample blocks to obtain an intermediate. The frozen sample block is preferably subjected to freeze drying treatment, so that ice crystals in the sample block sublimate into gas to escape, and the cellulose aerogel with oriented pore channels is obtained. In the present invention, the temperature of the freeze-drying is preferably-70 to-90 ℃, more preferably-70 to-80 ℃, and the time of the freeze-drying is preferably 24 to 72 hours, more preferably 36 to 72 hours.
And finally, performing heat treatment on the intermediate to obtain the cellulose aerogel. In the present invention, the intermediate is preferably placed in an oven for heat treatment so that the pore-forming agent is decomposed into a gas by heating, thereby imparting a microporous structure to the oriented pore surfaces of the cellulose aerogel. The temperature of the heat treatment is only required to ensure that the pore-forming agent can be decomposed on the premise of ensuring the stability of the cellulose aerogel, namely, the temperature of the heat treatment is lower than the decomposition temperature of the cellulose and higher than the decomposition temperature of the pore-forming agent, preferably 140-200 ℃, more preferably 140-180 ℃, and the time of the heat treatment is preferably 4-24 hours, more preferably 10-24 hours.
Compared with the prior art that cellulose is compounded with other materials or the cellulose is subjected to hydrophobic modification by utilizing petrochemical raw materials such as silane, the preparation method provided by the invention is environment-friendly, the whole process does not involve the use of petrochemical-based organic matters or polymers, only water and a small amount of carbon dioxide are discharged, the used experimental raw materials are nontoxic and harmless, the experimental raw materials can be obtained in batches, the cost is low, the obtained product can be completely degraded by biomass, and the industrial large-scale application is facilitated. The prepared cellulose aerogel material has excellent rebound resilience, can meet the requirement of large deformation such as folding, torsion and the like, and greatly improves the structural stability of the product so as to be suitable for different working scenes. Meanwhile, the obtained cellulose aerogel has excellent rebound resilience even at-196 ℃, so that the material can be used in extreme environments, such as space deep space.
The invention also provides a protective mask which comprises the cellulose aerogel or the cellulose aerogel prepared by the preparation method.
The protective mask of the present invention is not particularly limited, and preferably includes a cellulose aerogel, an upper support base fabric, a lower support base fabric, and a fixing member. The cellulose aerogel is attached to the upper supporting base fabric and the lower supporting base fabric, and two sides of the cellulose aerogel are fixed by fixing members.
The mask provided by the invention can be used for PM (particulate matter) under the condition that the gas flow rate is 1L/min 0.3 、PM 1.0 And PM 2.5 The filter material has excellent filtering effect, can be comparable with a commercial protective mask, has higher particle removal efficiency after being recycled for 10 ten thousand circles, and has excellent recycling performance.
In order to further illustrate the present invention, the following examples are provided. The experimental materials used in the following examples of the present invention are commercially available or prepared according to conventional preparation methods well known to those skilled in the art. Wherein, bacterial cellulose can be purchased from Gui Linji macro technology, and the model is BC aqueous dispersion; polyhydroxyalkanoate powder was purchased from Shandong Yikeman under the model P34HB.
Example 1
The embodiment provides a cellulose aerogel, and the preparation method thereof is as follows:
diluting bacterial cellulose nanofiber aqueous dispersion with water to 2mg/mL, taking 100mL of dispersion, adding 0.2g of polyhydroxyalkanoate powder, ball milling for 24 hours at a rotating speed of 200r/min to obtain uniform mixed dispersion, and removing bubbles by ultrasonic for later use;
placing a metal platform connected with a thermocouple in a plastic foam container, taking a through small block with the bottom surface of about 1.5cm x 1.5cm as a mould in the middle of a silica gel plate with the thickness of 1.5cm, flatly placing the mould on the surface of the metal platform, adding liquid nitrogen, and cooling to the top liquid in the mould at a constant speed by controlling the amount of the liquid nitrogen at a constant speed of 5 ℃/min to obtain a sample block after freezing. And taking out the sample block from the template, putting the sample block into a freeze dryer (the vacuum degree is 10Pa, the cold trap temperature is-80 ℃), taking out the sample block after 48 hours, and putting the sample block into a baking oven at 170 ℃ for 12 hours to obtain the cellulose aerogel.
Example 2
The embodiment provides a cellulose aerogel, and the preparation method thereof is as follows:
diluting bacterial cellulose nanofiber aqueous dispersion with water to 2mg/mL, taking 100mL of dispersion, adding 0.2g of polyhydroxyalkanoate powder, ball milling for 24 hours at a rotating speed of 200r/min to obtain uniform mixed dispersion, and removing bubbles by ultrasonic for later use;
placing a metal platform connected with a thermocouple in a plastic foam container, taking a through small block with the bottom surface of about 5cm to 5cm as a mould in the middle of a silica gel plate with the thickness of 1cm, placing the mould on the surface of the metal platform flatly, adding liquid nitrogen, and cooling to the top liquid in the mould at a constant speed of 5 ℃ per minute by controlling the amount of the liquid nitrogen, wherein freezing is considered to be finished, and obtaining a sample block. And taking out the sample block from the template, putting the sample block into a freeze dryer (the vacuum degree is 10Pa, the cold trap temperature is-80 ℃), taking out the sample block after 48 hours, and putting the sample block into a baking oven at 170 ℃ for 12 hours to obtain the cellulose aerogel.
Comparative example 1
This comparative example provides a disordered cellulose aerogel prepared by the following method:
diluting the bacterial cellulose nanofiber aqueous dispersion to 2mg/mL by adding water, pouring 100mL of the dispersion into a polydimethylsiloxane mould with square blank spaces of 1.5cm and immersing the polydimethylsiloxane mould in liquid nitrogen, and cooling the dispersion;
and taking out the sample blocks obtained after the freezing is finished, putting the sample blocks into a freeze dryer (the vacuum degree is 10Pa, the cold trap temperature is-80 ℃), and taking out the sample blocks after 48 hours to obtain the disordered cellulose aerogel.
Performance testing
The surface morphology of the pore-forming agent was characterized by using a scanning electron microscope, and as shown in fig. 1, it can be seen that the pore-forming agent is spherical particles, and as can be seen from the enlarged image of fig. 1, the pore-forming agent is formed by stacking smaller particles.
The aerogels obtained in example 1 and comparative example 1 were characterized for surface morphology using a scanning electron microscope, and the results are shown in fig. 2 to 3. Fig. 2 is an SEM image of a longitudinal section of the aerogel obtained in example 1, and fig. 3 is an SEM image of the aerogel obtained in comparative example 1. As can be seen from fig. 2-3, the resulting aerogel is disordered without the addition of pore formers and without the use of orientation freezing, and as can be seen from the enlarged image of fig. 2, there are substantially no micropores. In contrast, the aerogel obtained in example 1 had an oriented pore structure, and as can be seen from the enlarged image of fig. 3, the aerogel obtained in example 1 had many micropores.
The aerogels obtained in example 1 and comparative example 1 were mechanically tested using an Instron5565A universal tester (compression speed 5 mm/min), and the test results are shown in fig. 4, and it can be seen that in the cyclic stress-strain curve, the aerogel obtained in comparative example 1 had a compression stress of 0 when the compressive strain was 30% during rebound, and the aerogel obtained in example 1 had a compression stress of 0 when the compressive strain was substantially 0 during rebound, indicating that the aerogel material obtained in example 1 had more excellent rebound.
The aerogel obtained in example 1 and comparative example 1 was compressed to a deformation of 50%, and a comparison of which is shown in fig. 5, it can be seen that the aerogel material obtained in the present application has more excellent rebound resilience, which is consistent with the results obtained in the stress-strain curve described above.
The aerogel obtained in example 1 and comparative example 1 was twisted, and its actual comparison chart is shown in fig. 6, and it can be seen that the aerogel material obtained in the present application can satisfy large deformation such as twisting, and has excellent stability.
The aerogel obtained in example 1 was subjected to a bending experiment, and the physical diagram thereof is shown in fig. 7, so that it can be seen that the aerogel material obtained in the application can satisfy large deformation such as folding and has excellent stability.
The aerogel obtained in example 1 was placed in liquid nitrogen and the results are shown in fig. 8, and it can be seen that the aerogel material obtained in the present application has excellent resilience even in an environment of-196 ℃, making it possible to use the material in extreme environments, such as in the universe of deep space.
The aerogel obtained in example 1 was subjected to cyclic compression for 10 ten thousand cycles at 50% strain using an Instron5565A universal tester (compression speed 5 mm/min), and the stress strain curve is shown in fig. 9, so that it can be seen that the aerogel still has excellent rebound resilience performance after being subjected to cyclic compression for 10 ten thousand cycles at 50% strain.
Measurement of the PM on the cellulose aerogel obtained in example 2 with a commercial automatic filter tester (SC-FT-1406D-Plus, shi-dust purification technology Co., ltd.) at a gas flow rate of 1L/min 0.3 、PM 1.0 And PM 2.5 And can be compared with commercial protective masks. The results of the particle removal measured are shown in fig. 10, and it can be seen that the cellulose aerogel provided in the present application has excellent particle removal effect, which is comparable to that of the commercial protective mask.
PM of the cellulose aerogel obtained in example 2 was measured at an air flow rate of 1L/min using a commercial automatic filter tester (SC-FT-1406D-Plus, shi-dust purification technology Co., ltd.) 0.3 And PM 2.5 And the variation of the piezo-resistance with the number of cycles. As shown in FIG. 11, it can be seen that the particle removal efficiency and the piezoresistance of the cellulose aerogel provided by the application are not obvious along with the change of the cycle number, and the cellulose aerogel still has higher removal efficiency and excellent recycling performance even after being recycled for 10 ten thousands of cycles.
The previous description of the disclosed embodiments is provided to enable any person skilled in the art to make or use the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the invention. Thus, the present invention is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.
Claims (8)
1. The cellulose aerogel is characterized by comprising oriented pore channels and micropores distributed on the surfaces of the pore walls of the oriented pore channels;
the oriented pore channels are longitudinally distributed in the cellulose aerogel;
the preparation method of the cellulose aerogel comprises the following steps:
(1) Mixing cellulose, a pore-forming agent and water to obtain a dispersion;
(2) Orientation freezing is carried out on the dispersion liquid, and then the frozen sample block is dried to obtain an intermediate;
(3) Performing heat treatment on the intermediate to obtain cellulose aerogel;
the cellulose comprises bacterial cellulose and/or lignocellulose;
the pore-forming agent comprises polyhydroxyalkanoate P34HB;
the ratio of the cellulose, the pore-forming agent and the water is (0.05-1) g (90-120) mL;
the orientation freezing process is cooled at a speed of 1-10 ℃/min until the dispersion liquid is agglomerated;
the temperature of the heat treatment is 140-200 ℃, and the time of the heat treatment is 4-24 h.
2. The cellulose aerogel of claim 1, wherein the diameter of the oriented pore structure is 45-60 μm;
the aperture of the micropore is 0.5-2 mu m.
3. The method for preparing a cellulose aerogel according to claim 1 or 2, comprising the steps of:
(1) Mixing cellulose, a pore-forming agent and water to obtain a dispersion;
(2) Orientation freezing is carried out on the dispersion liquid, and then the frozen sample block is dried to obtain an intermediate;
(3) And performing heat treatment on the intermediate to obtain the cellulose aerogel.
4. The method according to claim 3, wherein the ratio of the cellulose, the pore-forming agent and water is (0.05-1) g (90-120) mL.
5. A method of preparation according to claim 3, wherein the orientation freezing process is cooled at a rate of 1-10 ℃/min until the dispersion agglomerates.
6. The method according to claim 3, wherein the freeze-drying temperature is-70 to-90 ℃, and the freeze-drying time is 24 to 72 hours.
7. A method according to claim 3, wherein the temperature of the heat treatment is 140 to 200 ℃ and the time of the heat treatment is 4 to 24 hours.
8. A protective mask comprising the cellulose aerogel of claim 1 or 2 or a cellulose aerogel prepared according to the method of any one of claims 3 to 7.
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