CN113527753A

CN113527753A - Bio-based foam material prepared under normal pressure and preparation method and application thereof

Info

Publication number: CN113527753A
Application number: CN202010293950.3A
Authority: CN
Inventors: 吴娜
Original assignee: Individual
Current assignee: Individual
Priority date: 2020-04-15
Filing date: 2020-04-15
Publication date: 2021-10-22
Anticipated expiration: 2040-04-15
Also published as: CN113527753B

Abstract

The invention provides a bio-based foam material prepared under normal pressure, a preparation method and application thereof, wherein the bio-based foam material comprises a cellulose substrate; the aperture of the bio-based foam material is 5-800 μm. The bio-based foam material has good lightweight property and mechanical strength, excellent human body affinity and biodegradability, and is a green and environment-friendly porous foam material. The bio-based foam material also comprises functional fillers and other additives, so that the bio-based foam material has wide application in the fields of mechanics, electrics, heat or biomedicine and the like. The bio-based foam material can be prepared at normal pressure, foaming equipment is not required to be adopted, a chemical foaming agent is not required to be added, special atmosphere is not required, equipment with higher requirements on vacuum degree, such as a freeze dryer and the like, is not required, the preparation process is simple, the operation cost is low, a support is not required, large-area large-scale production can be realized, and the bio-based foam material is suitable for large-scale industrial production.

Description

Bio-based foam material prepared under normal pressure and preparation method and application thereof

Technical Field

The invention belongs to the technical field of high polymer materials, and particularly relates to a bio-based foam material prepared under normal pressure, and a preparation method and application thereof.

Background

The foam material is a porous light material formed by dispersing a large number of gas micropores in a solid phase material, mainly comprises metal-based, carbon-based and polymer-based foam materials, and has the characteristics of heat insulation, light weight, sound absorption, shock absorption and the like. Most of the foam materials widely applied at present use chemical synthetic materials as matrixes, and the corresponding degradability and biocompatibility are lacked. Taking common polyurethane foam as an example, the polyurethane foam has poor biodegradability, high post-treatment cost and poor environmental protection. Therefore, the development of more environmentally friendly foams has become an urgent need.

Cellulose is a natural high molecular compound which is widely distributed and has the largest content in the nature, production raw materials are derived from wood, cotton linter, wheat straw, reed, hemp, mulberry bark, bagasse and the like, the cellulose foam material prepared by the cellulose foam material as the raw materials has attracted extensive attention by researchers in recent years. CN103131038A discloses a preparation method of a lignocellulose foam material, which comprises the following steps: firstly, smashing lignocellulose to obtain 20-200-mesh wood flour, and then adding the wood flour into water for grinding and dispersing to obtain a lignocellulose water dispersion liquid; and then carrying out freeze drying treatment on the lignocellulose aqueous dispersion to obtain the lignocellulose foam material. The preparation method is simple, the raw materials are low in price, the preparation cost is reduced, no pollution is caused, and the environment-friendly characteristic is realized. CN107915860A discloses a preparation method of a nano-cellulose microporous foam material, which comprises the following steps: dropwise adding concentrated sulfuric acid into the microcrystalline cellulose solution, stirring, centrifuging, performing ultrasonic treatment in an ice-water bath, and adjusting the pH value to be neutral to obtain a nanocrystalline cellulose (NCC) suspension; adding the NCC suspension into the PEG aqueous solution, uniformly mixing and carrying out vacuum drying to obtain a PEG/NCC composite filler; melting and blending PLA and PEG/NCC composite filler in an internal mixer to obtain a PLA/NCC composite material; and soaking the PLA/NCC composite material and the pure PLA material in supercritical carbon dioxide for decompression and foaming to obtain the PLA/NCC microporous foam material. The foam material obtained by the preparation method has uniform density, complete shape and uniform foam holes. CN105566659A discloses a graphene oxide/nanocellulose aerogel, and a preparation method and an application thereof, wherein the preparation method comprises the following steps: dispersing nano-cellulose in hydrochloric acid to prepare nano-cellulose dispersion liquid; uniformly mixing the graphene oxide dispersion liquid and the nano-cellulose dispersion liquid, and carrying out hydrothermal reaction at 170-190 ℃ to obtain hydrogel; and (3) freeze-drying the hydrogel to obtain the hydrogel. The aerogel has a porous structure with different diameters, and has a good removing effect on phenol in a phenol water solution.

In combination with the above prior art, the preparation process of the foam material at present mainly uses a physical and chemical foaming method, including a supercritical foaming method, a chemical vapor deposition method, a hydrothermal method or a freeze-drying method. However, these above-mentioned production methods often require high-energy-consumption and expensive equipment such as a precision reaction vessel, a chemical vapor deposition apparatus, a freeze dryer, and a supercritical injection molding machine; meanwhile, the above-mentioned preparation method has relatively severe requirements for molding operations or environments, such as requiring a special atmosphere (e.g., carbon dioxide or nitrogen), a specific gas pressure (e.g., vacuum), and a low-temperature or high-temperature environment; in addition, the existing preparation method of the foam material has limitations on the processing treatment of nano-scale or micron-scale materials, and is difficult to realize effective dispersion, for example, the nano-filler concentration in the polymer-based foam is low, the dispersion is poor, and the interface bonding capability is not strong. These limitations limit, to some extent, the large-scale preparation of foams and also limit the large-scale production and use of foams.

Therefore, the development of a foam material which is simple in preparation method, low in cost and energy consumption, green and environment-friendly is the research focus in the field.

Disclosure of Invention

Aiming at the defects of the prior art, the invention aims to provide a bio-based foam material prepared under normal pressure, a preparation method and application thereof.

In order to achieve the purpose, the invention adopts the following technical scheme:

in a first aspect, the present invention provides an ambient-prepared bio-based foam material comprising a cellulosic substrate; the pore size of the bio-based foam material is 5-800 μm, such as 6 μm, 8 μm, 10 μm, 11 μm, 13 μm, 15 μm, 16 μm, 18 μm, 20 μm, 25 μm, 30 μm, 35 μm, 40 μm, 45 μm, 50 μm, 55 μm, 60 μm, 65 μm, 70 μm, 75 μm, 80 μm, 85 μm, 90 μm, 95 μm, 100 μm, 110 μm, 120 μm, 130 μm, 140 μm, 150 μm, 160 μm, 170 μm, 180 μm, 190 μm, 200 μm, 220 μm, 250 μm, 280 μm, 300 μm, 320 μm, 350 μm, 380 μm, 400 μm, 420 μm, 450 μm, 480 μm, 500 μm, 550 μm, 520 μm, 580 μm, 620 μm, 650 μm, 780 μm, 650 μm, and 750 μm, or more specifically between the above points, the invention is not intended to be exhaustive or to list the specific point values included in the scope for brevity and clarity.

The bio-based foam material prepared under normal pressure provided by the invention takes cellulose as a matrix and can also comprise optional functional fillers and other additives, the functional fillers and other additives are uniformly dispersed in the cellulose matrix, and the cellulose is used as a dispersing agent, a cross-linking agent, an adhesive and a supporting and protecting matrix in the foam material.

Preferably, the bio-based foam material further comprises a functional filler.

Preferably, the content of the functional filler in the bio-based foam material is 0.5-90% by mass, such as 1%, 2%, 4%, 6%, 8%, 10%, 12%, 15%, 18%, 20%, 22%, 25%, 28%, 30%, 33%, 35%, 38%, 40%, 42%, 45%, 48%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85% or 88%, and the specific points between the above points are not exhaustive, and for brevity, the invention does not list the specific points included in the range, and more preferably 5-50%.

Preferably, the functional filler includes a metallic filler and/or a non-metallic filler.

Preferably, the functional filler is selected from any one of or a combination of at least two of carbon nanotubes, silver nanowires, copper nanowires, gold nanowires, carbon fibers, graphene, metal carbides, aluminum oxide, silicon carbide, carbon black, or MXenes.

Preferably, the functional filler is selected from any one of or a combination of at least two of carbon nanotubes, graphene, silver nanowires or silver microwires.

Preferably, the carbon nanotubes comprise any one of, or a combination of at least two of, single-walled carbon nanotubes, double-walled carbon nanotubes, or multi-walled carbon nanotubes.

In the present invention, the functional filler includes, but is not limited to, nano-scale or micro-scale functional particles, and the functional properties of the functional filler include, but are not limited to, electrical, thermal and mechanical properties. The introduction of the functional filler enables the bio-based foam material to be widely applied to the fields of structural materials, electronics and electricians and the like.

Preferably, the bio-based foam material further comprises other additives.

Preferably, the other additive comprises any one or a combination of at least two of an antibacterial agent, a reinforcing agent, a flame retardant, a thickener, a compatibilizer, a surfactant, an antioxidant, or a tackifier.

Preferably, the surfactant comprises sodium lauryl sulfate.

As a preferable technical scheme of the invention, the surfactant is added into the bio-based foam material, so that a pore structure with richer diameter distribution can be formed in the material. Specifically, a surfactant is added in the preparation of the bio-based foam material to foam in the aqueous dispersion, and then freezing and solvent replacement are carried out to obtain the bio-based foam material with a composite pore morphology of a mixture of large-aperture round pores and small-aperture pores.

Preferably, the antimicrobial agent comprises chlorhexidine and/or polyhexamethylene biguanide hydrochloride (PHMB).

Preferably, the other additives include any one of inorganic nanoparticles, inorganic microparticles, synthetic small molecules, or water-soluble polymers or a combination of at least two thereof.

In the present invention, the other additives include, but are not limited to, inorganic nano-particles, inorganic micro-particles, synthetic small molecules, polymers or biomolecules, etc. which are applied to the bio-based foam material as a flame retardant, a thickener, a compatibilizer, a surfactant, an antioxidant or an adhesion promoter.

Preferably, the other additive is selected from any one of lignin, sodium dodecyl sulfate, polyaniline, polyvinyl alcohol or polylactic acid or a combination of at least two of the same.

Preferably, the other additives include water-soluble polymers.

Preferably, the other additive is selected from any one of starch, vegetable gum, animal gum, hydroxymethyl starch, starch acetate, hydroxymethyl cellulose, carboxymethyl cellulose, polyacrylamide, aqueous polyurethane, polyvinylpyrrolidone, polyacrylic acid, polyacrylate, polyvinyl alcohol, polymaleic anhydride or polyethylene glycol or a combination of at least two of the above.

Preferably, the pore size of the bio-based foam material is 5-200 μm.

Preferably, the cell morphology of the bio-based foam material comprises any one or a combination of at least two of a lamellar cell morphology, a honeycomb cell morphology, or a random cell morphology.

Preferably, the random apertures comprise circular apertures.

In the invention, the density of the bio-based foam material is 5-800 mg/cm³E.g. 6mg/cm³、8mg/cm³、10mg/cm³、15mg/cm³、20mg/cm³、25mg/cm³、30mg/cm³、35mg/cm³、40mg/cm³、45mg/cm³、50mg/cm³、55mg/cm³、60mg/cm³、65mg/cm³、70mg/cm³、75mg/cm³、80mg/cm³、85mg/cm³、90mg/cm³、95mg/cm³、100mg/cm³、150mg/cm³、200mg/cm³、250mg/cm³、300mg/cm³、350mg/cm³、400mg/cm³、450mg/cm³、500mg/cm³、550mg/cm³、600mg/cm³、650mg/cm³、700mg/cm³、750mg/cm³Or 780mg/cm³And the specific values between the above-mentioned values, are limited by space and for the sake of brevity, the invention is not intended to be exhaustive of the specific values included in the range, preferably 8-100 mg/cm³More preferably 10 to 70mg/cm³。

Preferably, the cellulose of the cellulose matrix comprises lignocellulose and/or bacterial cellulose, further preferably lignocellulose.

Preferably, the cellulose of the cellulose matrix comprises cellulose nanofibers and/or cellulose microfibers.

In the present invention, the cellulose of the cellulose substrate includes, but is not limited to, nano or micro cellulose fibers.

In another aspect, the present invention provides a method for preparing a bio-based foam material as described above, comprising the steps of:

(1) mixing cellulose and water, and uniformly dispersing to obtain a water dispersion;

(2) freezing the aqueous dispersion obtained in the step (1) to obtain a solidified sample;

(3) and (3) mixing the solidified sample obtained in the step (2) with an organic solvent, melting and solvent replacement of the solidified sample in the organic solvent, and drying at normal pressure to obtain the bio-based foam material.

In the preparation method provided by the invention, the raw material components are mixed with water and uniformly dispersed to obtain an aqueous dispersion, and then the aqueous dispersion is frozen to be solidified; and (3) placing the solidified sample in an organic solvent, melting the solidified sample in the organic solvent, carrying out solvent replacement, completely replacing water in the sample with the organic solvent, and drying at normal pressure to obtain the bio-based foam material. The preparation method can complete the preparation of the foam material under normal pressure without adopting foaming equipment, adding a chemical foaming agent, adding a special atmosphere or using equipment with higher requirements on vacuum degree, such as a freeze dryer and the like, thereby greatly reducing the energy consumption and equipment cost and providing a brand new idea for large-scale industrial production of the foam material.

Preferably, the mixing in step (1) further comprises a functional filler and/or other additives.

Preferably, the cellulose of step (1) comprises cellulose nanofibers and/or cellulose microfibers.

Preferably, the concentration of the dispersoid in the aqueous dispersion of step (1) is 0.1 to 50 wt%, such as 0.2 wt%, 0.4 wt%, 0.6 wt%, 0.8 wt%, 1 wt%, 2 wt%, 3 wt%, 4 wt%, 5 wt%, 6 wt%, 7 wt%, 8 wt%, 9 wt%, 10 wt%, 12 wt%, 14 wt%, 15 wt%, 17 wt%, 19 wt%, 20 wt%, 22 wt%, 24 wt%, 25 wt%, 27 wt%, 29 wt%, 30 wt%, 32 wt%, 35 wt%, 38 wt%, 40 wt%, 42 wt%, 45 wt%, 47 wt%, or 49 wt%, and specific points therebetween are not exhaustive and for the sake of brevity, and specific points included in the range are not enumerated herein.

In the present invention, the concentration of the dispersoid in the aqueous dispersion is the total concentration of the dispersoid, and the dispersoid comprises cellulose and optional functional fillers and other additives. The functional filler and/or other additives may be used in amounts that meet the performance requirements of the bio-based foam.

Preferably, the dispersion in step (1) can be assisted by magnetic stirring or ultrasound, so that the raw material components are uniformly dispersed in water.

Preferably, the temperature of the freezing treatment in the step (2) is less than or equal to-20 ℃.

Preferably, the freezing treatment method in the step (2) comprises refrigerator freezing, liquid nitrogen freezing, dry ice freezing or liquid helium freezing.

Preferably, the time of the freezing treatment in the step (2) is 0.1 to 3 hours, such as 0.2h, 0.4h, 0.5h, 0.7h, 0.9h, 1h, 1.2h, 1.4h, 1.5h, 1.7h, 1.9h, 2h, 2.2h, 2.4h, 2.5h, 2.7h or 2.9h, and the specific values therebetween are limited by space and simplicity, and the invention is not exhaustive list of the specific values included in the range, and further preferably 10 to 60 min.

Preferably, the freezing process of step (2) comprises directional freezing.

Preferably, the directional freezing is achieved by a mold, the main body material of which is a silicone rubber mold, the bottom of which is metal (e.g., copper). When the aqueous dispersion obtained in the step (1) is placed in the mould and is placed in a freezing environment, a unidirectional temperature gradient is generated in the system, ice crystals grow along the gradient, and dispersoids in the dispersion are removed and adsorbed on the surfaces of the ice crystals. The directional freezing can finally obtain the bio-based foam material with cellular pore morphology.

In the present invention, the organic solvent in step (3) is selected from any one or a combination of at least two of ethanol, ethylene glycol, acetone, dichloromethane, tetrachloromethane, chloroform, and methyl pyrrolidone, preferably acetone and/or ethanol, and more preferably ethanol.

Preferably, the mixing of step (3) is carried out at room temperature.

Preferably, the temperature of the atmospheric drying in the step (3) is 15 to 180 ℃, for example, 18 ℃, 20 ℃, 23 ℃, 25 ℃, 28 ℃, 30 ℃, 32 ℃, 35 ℃, 38 ℃, 40 ℃, 42 ℃, 45 ℃, 48 ℃, 50 ℃, 52 ℃, 55 ℃, 58 ℃, 60 ℃, 65 ℃, 70 ℃, 75 ℃, 80 ℃, 85 ℃, 90 ℃, 95 ℃, 100 ℃, 105 ℃, 110 ℃, 115 ℃, 120 ℃, 125 ℃, 130 ℃, 135 ℃, 140 ℃, 145 ℃, 150 ℃, 155 ℃, 160 ℃, 165 ℃, 170 ℃ or 175 ℃, and the specific values therebetween are limited to the space and for the sake of brevity, and the invention is not exhaustive.

In the present invention, the drying under normal pressure in step (3) may be performed at room temperature or may be performed in a heating device such as an oven.

Preferably, the organic solvent in step (3) further comprises a modifier.

Preferably, the modifier is a hydrophobic modifier.

Preferably, the hydrophobic modifier is a combination of 4,4' -phenyl isocyanate and trimethylamine, wherein the trimethylamine is a catalyst.

Preferably, the preparation method specifically comprises the following steps:

(1) mixing cellulose, functional filler and optional other additives with water and uniformly dispersing to obtain an aqueous dispersion with the dispersoid concentration of 0.1-50 wt%;

In another aspect, the present invention provides a use of the bio-based foam material as described above in an electromagnetic shielding material, a buffering material, an electro-thermal material, a fireproof material, a low thermal conductive material, a thermal insulating material, a filtering material, a building material, a packaging material, a biomedical material, an antibacterial material, or a supporting material.

Compared with the prior art, the invention has the following beneficial effects:

(1) the bio-based foam material prepared under normal pressure provided by the invention takes cellulose as a matrix, has good lightweight property and mechanical strength, excellent human body affinity and biodegradability, and is a green and environment-friendly porous foam material.

(2) The bio-based foam material also comprises functional fillers and other additives, and the content of the functional fillers and other additives can be adjusted according to the application requirements of the material, so that the bio-based foam material has wide application in the fields of mechanics, electricity, heat or biological medicine and the like.

(3) The bio-based foam material provided by the invention can be prepared at normal pressure, foaming equipment is not required to be adopted, a chemical foaming agent is not required to be added, special atmosphere is not required, equipment with higher requirements on vacuum degree, such as a freeze dryer and the like, is not required to be used, the preparation process is simple, the operation cost is low, a support is not required to be relied on, large-area large-scale production can be realized, and the bio-based foam material is suitable for large-scale industrial production.

Drawings

FIG. 1 is an optical photograph of the bio-based foam material provided in example 1;

FIG. 2 is a scanning electron micrograph of the bio-based foam provided in example 8;

FIG. 3 is a scanning electron micrograph of the bio-based foam provided in example 13;

FIG. 4 is a scanning electron micrograph of the bio-based foam provided in example 15;

FIG. 5 is a scanning electron micrograph of the bio-based foam provided in example 16;

FIG. 6 is a scanning electron micrograph of a bio-based foam provided in example 17;

FIG. 7 is a scanning electron micrograph of the bio-based foam provided in example 18;

FIG. 8 is a scanning electron micrograph of a bio-based foam provided in example 19;

FIG. 9 is a surface contact angle test chart of the bio-based foam provided in example 20;

FIG. 10 is a graph of the electrogenerated heating effect of the bio-based foam provided in example 12;

FIG. 11 is a graph showing the antibacterial property test of the bio-based foam provided in example 14;

fig. 12 is a graph illustrating the absorption performance test of the bio-based foam provided in example 1.

Detailed Description

The technical solution of the present invention is further explained by the following embodiments. It should be understood by those skilled in the art that the examples are only for the understanding of the present invention and should not be construed as the specific limitations of the present invention.

Examples 1 to 5

A bio-based foam material prepared under normal pressure is prepared by the following steps:

(1) mixing functional filler carbon nanotube powder, cellulose and water to ensure that the concentration of the carbon nanotubes in a mixed system is 1.5 wt% and the concentration of the cellulose is 0.5 wt%, performing ultrasonic treatment to assist the dispersion of the carbon nanotubes, further stirring for 2.5 hours by using a magnetic stirrer, and uniformly mixing to obtain a dispersion solution I;

(2) mixing and dispersing cellulose and water to obtain a dispersion liquid II with the cellulose content of 2.0 wt%;

(3) mixing the dispersion liquid I obtained in the step (1) and the dispersion liquid II obtained in the step (2) according to a proportion, and uniformly stirring and dispersing the mixture, wherein the specific mixing ratio is shown in the following table 1, so as to obtain water dispersion liquids with different carbon nano tube concentrations;

(4) putting the aqueous dispersion obtained in the step (3) into a polytetrafluoroethylene die with the length of 40cm and the width of 28cm, and freezing for 3 hours in a refrigerator with the temperature of-20 ℃ to obtain a solidified sample;

(5) mixing the solidified sample obtained in the step (4) with ethanol at room temperature to melt the solidified sample in the ethanol and realize solvent replacement, absorbing the solvent in the system, and drying at room temperature overnight to obtain the sizeIs 40X 28X 2cm³The bio-based foam material of (1), namely, the carbon nanotube-cellulose composite foam material, wherein an optical picture of the bio-based foam material provided in example 1 is shown in fig. 1.

TABLE 1

As can be seen from the preparation steps and table 1, in the carbon nanotube-cellulose composite foam materials provided in examples 1 to 5, the bio-based foam materials with different carbon nanotube contents are obtained by adjusting the volume ratio of the dispersion liquid I to the dispersion liquid II.

Examples 6 to 11

(1) mixing functional filler carbon nanotube powder, cellulose and water to ensure that the concentration of the carbon nanotubes in a mixed system is 2.5 wt% and the concentration of the cellulose is 2.5 wt%, performing ultrasonic treatment to assist the dispersion of the carbon nanotubes, further stirring for 3 hours by using a magnetic stirrer, and uniformly mixing to obtain a dispersion liquid I;

(2) mixing the dispersion I obtained in the step (1) with water, and uniformly stirring and dispersing the mixture, wherein the specific mixing ratio is shown in the following table 2, so as to obtain water dispersions with different dispersoid concentrations;

(3) placing the aqueous dispersion obtained in the step (2) in a mould, and freezing for 1.5h in a refrigerator at the temperature of-30 ℃ to obtain a solidified sample;

(4) and (4) mixing the solidified sample obtained in the step (3) with acetone at room temperature, melting the solidified sample in the acetone, realizing solvent replacement, absorbing the solvent in the system, and drying in an oven at the temperature of 80 ℃ for 2 hours under normal pressure to obtain the bio-based foam material, namely the carbon nano tube-cellulose composite foam material.

TABLE 2

As can be seen from the preparation steps and table 2, in the carbon nanotube-cellulose composite foam materials provided in examples 6 to 11, bio-based foam materials with different densities are obtained by adjusting the volume ratio of the dispersion liquid I to water.

The above biobased foam was tested by scanning electron microscopy (SEM, JSM-7600F), wherein the density obtained in example 8 was 20mg/cm³The scanning electron microscope image of the bio-based foam material is shown in fig. 2.

Example 12

(1) mixing functional filler carbon nanotube powder, cellulose and water, performing ultrasonic treatment to assist the dispersion of the carbon nanotubes, stirring for 2 hours by using a magnetic stirrer, and uniformly mixing to obtain a dispersion liquid I; adding other additives of nano silicon dioxide dispersed in water into the dispersion solution I, further stirring and uniformly dispersing to obtain an aqueous dispersion solution with the concentration of the carbon nano tubes of 1.0 wt%, the concentration of the cellulose of 0.8 wt% and the concentration of the nano silicon dioxide of 0.2 wt%;

(2) putting the aqueous dispersion obtained in the step (1) into a polytetrafluoroethylene die with the length of 40cm and the width of 28cm, and freezing for 3 hours in a refrigerator at the temperature of-20 ℃ to obtain a solidified sample;

(3) mixing the solidified sample obtained in the step (2) with ethanol at room temperature to melt the solidified sample in the ethanol and realize solvent replacement, absorbing the solvent in the system, and drying in an oven at 80 ℃ under normal pressure for 3h to obtain the product with the size of 40 multiplied by 28 multiplied by 2cm³I.e., a carbon nanotube-cellulose composite foam containing a flame retardant silica.

Example 13

(1) mixing silver nanowires (with the average diameter of 50nm and the length of 10-40 mu m) and silver nanoparticles (with the average particle size of 50nm) as functional fillers, cellulose and water, stirring for 2.5 hours by using a magnetic stirrer, and uniformly mixing to obtain an aqueous dispersion with the silver nanowire concentration of 0.2 wt%, the silver nanoparticle concentration of 0.05 wt% and the cellulose concentration of 1.75 wt%;

(2) placing the aqueous dispersion obtained in the step (1) in a mould, and freezing for 3h in a refrigerator at the temperature of-20 ℃ to obtain a solidified sample;

(3) and (3) mixing the solidified sample obtained in the step (2) with ethanol at room temperature, melting the solidified sample in the ethanol, realizing solvent replacement, absorbing the solvent in the system, and drying overnight at room temperature to obtain a bio-based foam material, namely the silver nanowire-silver nanoparticle-cellulose composite foam material, wherein the mass percentage of the silver nanowire in the bio-based foam material is 10%, and the mass percentage of the silver nanoparticle in the bio-based foam material is 2.5%.

The bio-based foam material obtained in this example was tested by scanning electron microscopy (SEM, JSM-7600F) and the obtained scanning electron microscopy picture is shown in FIG. 3.

Example 14

(1) mixing functional filler silver nanowires (with the average diameter of 50nm and the length of 10-40 mu m) and cellulose with water, stirring for 2.5 hours by using a magnetic stirrer, and uniformly mixing to obtain an aqueous dispersion with the silver nanowire concentration of 0.2 wt% and the cellulose concentration of 1.8 wt%;

(2) placing the aqueous dispersion obtained in the step (1) in a mould, and freezing the aqueous dispersion in a refrigerator at the temperature of-20 ℃ for 2.5 hours to obtain a solidified sample;

(3) and (3) mixing the solidified sample obtained in the step (2) with ethanol at room temperature, melting the solidified sample in the ethanol, realizing solvent replacement, absorbing the solvent in the system, and drying in a 50 ℃ oven for 3 hours to obtain a bio-based foam material, namely the silver nanowire-cellulose composite foam material, wherein the mass percentage of the silver nanowires in the bio-based foam material is 10%.

In addition, by adjusting the addition amount of the silver nanowires in the step (1) of the embodiment, an aqueous dispersion with a silver nanowire concentration of 0.001-1.5 wt% can be obtained, and then bio-based foam materials with different silver nanowire contents can be obtained. Moreover, the silver nanowires in step (1) of this example can be replaced with silver nanoparticles, thereby obtaining a silver nanoparticle-cellulose composite foam material.

Example 15

(1) mixing functional filler graphene, cellulose and water, stirring for 2.5 hours by using a magnetic stirrer, and uniformly mixing to obtain an aqueous dispersion with the graphene concentration of 1.0 wt% and the cellulose concentration of 1.0 wt%;

(2) placing the aqueous dispersion obtained in the step (1) in a mould, and freezing for 1h in a refrigerator at the temperature of-40 ℃ to obtain a solidified sample;

(3) and (3) mixing the solidified sample obtained in the step (2) with ethanol at room temperature, melting the solidified sample in the ethanol, realizing solvent replacement, absorbing the solvent in the system, and drying overnight at room temperature to obtain the bio-based foam material, namely the graphene-cellulose composite foam material.

The bio-based foam material obtained in this example was tested by scanning electron microscopy (SEM, JSM-7600F) and the obtained scanning electron microscopy picture is shown in FIG. 4.

In addition, by adjusting the addition amount of the graphene in the step (1) in this embodiment, an aqueous dispersion with a graphene concentration of 0.01 to 1.5 wt% can be obtained, and then bio-based foam materials with different graphene contents can be obtained.

Example 16

(1) mixing functional filler carbon nanotube powder, cellulose and water, performing ultrasonic treatment to assist the dispersion of the carbon nanotubes, stirring for 2.5 hours by using a magnetic stirrer, and uniformly mixing to obtain an aqueous dispersion with the concentration of the carbon nanotubes of 1.0 wt% and the concentration of the cellulose of 1.0 wt%;

(2) placing the aqueous dispersion obtained in the step (1) in a silicon rubber mold, and freezing for 30min in a refrigerator at the temperature of-80 ℃ to obtain a solidified sample;

(3) and (3) mixing the solidified sample obtained in the step (2) with ethanol at room temperature, melting the solidified sample in the ethanol, realizing solvent replacement, absorbing the solvent in the system, and drying overnight at room temperature to obtain the bio-based foam material, namely the carbon nano tube-cellulose composite foam material.

The bio-based foam material obtained in this example is tested by a scanning electron microscope (SEM, JSM-7600F), and the obtained scanning electron microscope picture is shown in fig. 5, and it can be known from the preparation steps and fig. 5 that the carbon nanotube-cellulose composite foam material provided in this example has a random pore morphology.

Example 17

A bio-based foam material prepared under normal pressure, which is prepared by the steps different from the embodiment 16 only in that the mold in the step (2) is a silicone rubber mold with a metal copper bottom, an aqueous dispersion is placed in the silicone rubber mold with the metal copper bottom, and is frozen in dry ice for 10min, so that a unidirectional temperature gradient is generated in the aqueous dispersion, ice crystals are produced along the gradient, and dispersoids in the dispersion are removed and adsorbed on the surface of the ice crystals, and a solidified sample is obtained; the other preparation steps were the same as in example 16.

The bio-based foam material obtained in this example is tested by a scanning electron microscope (SEM, JSM-7600F), and the obtained scanning electron microscope picture is shown in fig. 6, and it can be known from the preparation steps and fig. 6 that the carbon nanotube-cellulose composite foam material provided in this example has a honeycomb-shaped pore morphology with an average pore diameter of 60 μm.

Example 18

A bio-based foam material prepared under normal pressure, which is prepared by the steps different from the embodiment 16 only in that the mold in the step (2) is a silicone rubber mold with a metal copper bottom, the aqueous dispersion is placed in the silicone rubber mold with the metal copper bottom, and is frozen in a refrigerator at-20 ℃ for 120min, so that a unidirectional temperature gradient is generated in the aqueous dispersion, ice crystals are produced along the gradient, and dispersoids in the dispersion are removed and adsorbed on the surface of the ice crystals, so as to obtain a solidified sample; the other preparation steps were the same as in example 16.

The bio-based foam material obtained in this example is tested by a scanning electron microscope (SEM, JSM-7600F), and the obtained scanning electron microscope picture is shown in fig. 7, and it can be known from the above preparation steps and fig. 7 that the carbon nanotube-cellulose composite foam material provided in this example has a honeycomb-shaped pore morphology with a larger pore diameter, and the average pore diameter is 150 μm.

Example 19

(1) mixing functional filler carbon nanotube powder, cellulose and water, performing ultrasonic treatment to assist the dispersion of the carbon nanotubes, further adding surfactant Sodium Dodecyl Sulfate (SDS), stirring by using a magnetic stirrer, and uniformly mixing to obtain an aqueous dispersion with the concentration of the carbon nanotubes of 1.0 wt%, the concentration of the SDS of 0.1 wt% and the concentration of the cellulose of 1.0 wt%, wherein the SDS foams the aqueous dispersion;

(2) placing the aqueous dispersion obtained in the step (1) in a silicon rubber mould with metal copper at the bottom, freezing the aqueous dispersion in dry ice for 10min to generate a unidirectional temperature gradient in the aqueous dispersion, producing ice crystals along the gradient, and removing and adsorbing dispersoids in the dispersion on the surface of the ice crystals to obtain a solidified sample;

(3) and (3) mixing the solidified sample obtained in the step (2) with ethanol at room temperature, melting the solidified sample in the ethanol, realizing solvent replacement, absorbing the solvent in the system, and drying overnight at room temperature to obtain the bio-based foam material.

The bio-based foam material obtained in this example was tested by scanning electron microscopy (SEM, JSM-7600F) and the obtained scanning electron microscopy picture is shown in FIG. 8. As can be seen from the above preparation steps and fig. 8, the bio-based foam material provided in this embodiment has a mixed pore morphology of round pores and oriented pores, wherein the pore diameter of the round pores reaches 400 μm, the pores are generated based on the surfactant introduced in step (1), and the average pore diameter of the oriented pores is 20 μm.

Example 20

(2) placing the aqueous dispersion obtained in the step (1) in a silicon rubber mold, and freezing for 1h in a refrigerator at the temperature of-30 ℃ to obtain a solidified sample;

(3) mixing the solidified sample obtained in the step (2) with acetone at room temperature, adding a combination of a hydrophobic modifier 4,4 '-phenyl isocyanate and trimethylamine into the acetone, enabling the 4,4' -phenyl isocyanate and hydroxyl functional groups on the surfaces of the cellulose fibers to fully react under the catalysis of the trimethylamine to form ester bonds, melting the solidified sample in the acetone and performing solvent replacement while the reaction is carried out, sucking off the solvent in the system after the replacement is finished, and drying the solidified sample in an oven at 80 ℃ for 2 hours under normal pressure to obtain the hydrophobic modified biological-based foam material.

Fig. 9 shows a surface contact angle test chart obtained by testing the bio-based foam material obtained in the present embodiment with a contact angle measuring instrument, and as can be seen from fig. 9, the surface contact angle of the hydrophobically modified bio-based foam material provided in the present embodiment reaches 110 ° or more, and has good hydrophobicity.

Test example 1

This test example is a test experiment for testing the electric heating property of the bio-based foam material provided in example 12, and the specific test steps are as follows:

the bio-based foam material provided in example 12 (containing 50% carbon nanotubes and 10% silicon dioxide) was cut and applied to electrodes with a 30mm pitch using silver paste; voltage was applied between the electrodes, spot temperature measurements were taken on the surface using a thermocouple, temperature was recorded versus time and plotted, and the resulting graph of the effect of the electroluminescence is shown in fig. 10.

As can be seen from FIG. 10, the bio-based foam material can be raised to different temperatures and kept stable under different voltages, and the voltage is applied for a plurality of times for a long time, so that the obtained curve has good repeatability, the foam material has good temperature rise stability, and the response time required for raising the temperature to 80% of the maximum temperature is short. Therefore, the bio-based foam material provided by the invention can quickly and stably heat and raise the temperature under low voltage.

Test example 2

The test example is a test experiment for the antibacterial performance of the bio-based foam material provided in example 14, and the specific test steps are as follows:

the bio-based foam material provided in example 14 (containing 10% silver nanowires) was placed in a culture medium, and staphylococcus aureus (s. After 24h, the growth of the bacteria was observed, and the obtained antibacterial property test chart is shown in FIG. 11.

As can be seen from fig. 11, 2 pieces of the bio-based foam material provided by the present invention were placed in the petri dish, and no bacteria grew on the surface and the peripheral area of the bio-based foam material, and the bacteria could not survive, which proves that the bio-based foam material has good antibacterial performance.

Test example 3

The test example is a test experiment of the adsorption performance of the bio-based foam material provided in example 1, and the specific test steps are as follows:

the bio-based foam material provided by the embodiment 1 is placed in a methyl blue solution, the bio-based foam material is taken out after standing for 24h, the methyl blue solution before and after the bio-based foam material is placed is observed, and the obtained adsorption performance test chart is shown in fig. 12, and as can be seen from fig. 12, the bio-based foam material provided by the invention has excellent adsorption performance on organic dyes, because the bio-based foam material has high porosity, the material can effectively adsorb the organic dyes; the adsorption efficiency of the bio-based foam material to methyl blue can be quantitatively measured by using an ultraviolet spectrum, and the adsorption rate can reach 100 percent, so that the bio-based foam material provided by the invention can be used as a high-performance adsorption material.

The applicant states that the present invention is illustrated by the above examples, but the present invention is not limited to the above process steps, i.e. it does not mean that the present invention must rely on the above process steps to be carried out. It will be apparent to those skilled in the art that any modification of the present invention, equivalent substitutions of selected materials and additions of auxiliary components, selection of specific modes and the like, which are within the scope and disclosure of the present invention, are contemplated by the present invention.

Claims

1. An ambient pressure prepared bio-based foam material, characterized in that the bio-based foam material comprises a cellulose matrix; the aperture of the bio-based foam material is 5-800 μm.

2. The bio-based foam material according to claim 1, wherein the bio-based foam material further comprises a functional filler;

preferably, the mass percentage of the functional filler in the bio-based foam material is 0.5-90%, and more preferably 5-50%;

preferably, the functional filler comprises a metallic filler and/or a non-metallic filler;

preferably, the functional filler is selected from any one or a combination of at least two of carbon nanotubes, silver nanowires, copper nanowires, gold nanowires, carbon fibers, graphene, metal carbides, aluminum oxide, silicon carbide, carbon black, or MXenes;

preferably, the functional filler is selected from any one or a combination of at least two of carbon nanotubes, graphene, silver nanowires or silver microwires;

3. The bio-based foam material according to claim 1 or 2, wherein the bio-based foam material further comprises other additives;

preferably, the other additives include any one or a combination of at least two of an antibacterial agent, a reinforcing agent, a flame retardant, a thickener, a compatibilizer, a surfactant, an antioxidant, or a tackifier;

preferably, the antimicrobial agent comprises chlorhexidine and/or polyhexamethylene biguanide hydrochloride;

preferably, the surfactant comprises sodium lauryl sulfate;

4. The bio-based foam material according to any one of claims 1 to 3, wherein the bio-based foam material has a pore size of 5 to 200 μm;

5. The bio-based foam material according to any one of claims 1 to 4, wherein the density of the bio-based foam material is 5 to 800mg/cm³Preferably 8 to 100mg/cm³More preferably 10 to 70mg/cm³；

Preferably, the cellulose of the cellulose matrix comprises cellulose nanofibers and/or cellulose microfibers;

6. A method of preparing a bio-based foam material according to any one of claims 1 to 5, wherein the method comprises the steps of:

7. The method of claim 6, wherein the mixing of step (1) further comprises a functional filler and/or other additives;

preferably, the cellulose of step (1) comprises cellulose nanofibers and/or cellulose microfibers;

preferably, the concentration of the dispersoid in the aqueous dispersion of the step (1) is 0.1 to 50 weight percent;

preferably, the temperature of the freezing treatment in the step (2) is less than or equal to-20 ℃;

preferably, the freezing treatment method in the step (2) comprises refrigerator freezing, liquid nitrogen freezing, dry ice freezing or liquid helium freezing;

preferably, the time of the freezing treatment in the step (2) is 0.1-3 h, and further preferably 10-60 min;

preferably, the freezing process of step (2) comprises directional freezing.

8. The production method according to claim 6 or 7, wherein the organic solvent in step (3) is selected from any one or a combination of at least two of ethanol, ethylene glycol, acetone, dichloromethane, tetrachloromethane, chloroform, or methylpyrrolidone, preferably acetone and/or ethanol, and more preferably ethanol;

preferably, the mixing of step (3) is carried out at room temperature;

preferably, the temperature of the atmospheric drying in the step (3) is 15-180 ℃;

preferably, the organic solvent in the step (3) further comprises a modifier;

preferably, the modifier is a hydrophobic modifier.

9. The preparation method according to any one of claims 6 to 8, characterized by specifically comprising the steps of:

10. Use of the bio-based foam material according to any one of claims 1 to 5 in electromagnetic shielding materials, cushioning materials, electric heating materials, fire-proof materials, low thermal conductivity materials, thermal insulation materials, filter materials, building materials, packaging materials, biomedical materials, antibacterial materials or support materials.