CN116790029A - Preparation method of polybenzoxazine@cellulose nanofiber high-strength aerogel - Google Patents
Preparation method of polybenzoxazine@cellulose nanofiber high-strength aerogel Download PDFInfo
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- ZMXDDKWLCZADIW-UHFFFAOYSA-N N,N-Dimethylformamide Chemical compound CN(C)C=O ZMXDDKWLCZADIW-UHFFFAOYSA-N 0.000 claims description 27
- OKKJLVBELUTLKV-UHFFFAOYSA-N Methanol Chemical compound OC OKKJLVBELUTLKV-UHFFFAOYSA-N 0.000 claims description 21
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- 230000021523 carboxylation Effects 0.000 claims 1
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- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 abstract description 3
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- 229910018072 Al 2 O 3 Inorganic materials 0.000 description 3
- SECXISVLQFMRJM-UHFFFAOYSA-N N-Methylpyrrolidone Chemical compound CN1CCCC1=O SECXISVLQFMRJM-UHFFFAOYSA-N 0.000 description 3
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Abstract
The invention discloses a preparation method of polybenzoxazine@cellulose nanofiber high-strength aerogel, which comprises the following steps: adding a benzoxazine monomer with a specific structure into a mixed solvent dispersion liquid of cellulose nanofiber, and stirring at a certain speed until the benzoxazine monomer is completely dissolved; secondly, after adding the hydrophobic modifier and the photocatalyst, promoting the benzoxazine monomer in the step S1 to partially open the ring through photocatalysis induction so as to limit the cellulose nanofiber in a partially formed gel structure, and avoiding agglomeration caused by subsequent severe reaction; thirdly, promoting the ring-opening polymerization reaction of the benzoxazine monomer to be complete by a hydrothermal auxiliary sol-gel method; fourth, removing impurities and replacing solvents from the wet gel obtained in the third step; fifth, the alcohol obtained in the fourth step is reacted withPlacing the gel in a protective solution for supercritical CO 2 And (5) drying.
Description
Technical Field
The invention belongs to the technical field of functional nano porous materials, and particularly relates to a preparation method of a polybenzoxazine@cellulose nanofiber high-strength aerogel.
Background
Due to high specific surface area, low density, high porosity and connectivityThe aerogel has been receiving a great deal of attention from the birth date due to the structural advantages of the network skeleton, and is expected to be used in the fields of heat insulation, catalysis, medicine, construction, aerospace and the like. However, the poor structural continuity and the point-to-point rigidity between the secondary particles cause mechanical performance limitations such as low strength, high brittleness, poor processability and the like, and limit the development and application of the aerogel in various large fields. In order to make the aerogel serve the development of socioeconomic as soon as possible, researchers have developed a positive attack on "high strength aerogel" and have achieved some staged results, wherein, in Al 2 O 3 C high strength aerogel research systems are most common. High temperature treatment can induce Al 2 O 3 Is enhanced and the neck region between the C nanoparticles is expanded ([ 1)]Secondary, kong Yong, shen Xiaodong, et al, university of south Beijing industry, university report 2012, 34, 26-30; [2]Z.Yang, J.Li, X.Xu, et Al, J.Mater.Sci.Technol.,2020, 50, 66-74), prepared Al 2 O 3 C and the composite aerogel thereof can show higher strength, and the defect of aerogel materials in low strength is overcome to a certain extent. However, high temperature treatment also results in increased brittleness, which in turn results in reduced utility value.
The benzoxazine is a generic name of a compound containing N and O six-membered oxazine rings in a structure, is a novel thermosetting resin, has almost zero curing shrinkage, high modulus, high strength, good heat resistance, low water absorption and other performance characteristics because no small molecules are released in the curing process, has the concept of the benzoxazine high-strength aerogel, and is also developed in succession in the research related to the field. The university of national defense science and technology selects a series of benzoxazine monomers to successfully prepare different types of polybenzoxazine aerogel (Feng Jian, shourua, jiang Yonggang and the like. Polybenzoxazine aerogel heat insulation materials and a preparation method thereof [ P ]. CN108690191B, 2020-10-09) prove the feasibility and rationality of the polybenzoxazine as a high-strength aerogel research system. The university of electronic technology uses a hydrogen bond system in the polybenzoxazine as a research basis, and the mechanical property of the polybenzoxazine aerogel is further enhanced by constructing a larger reversible sacrificial hydrogen bond network ([ 1] Liao Guxuan, longxin, zhang Lingzhao.) the preparation method of the polybenzoxazine aerogel with high strength and toughness [ P ]. CN116396527A; [2]X.Long,P.Tang,L.Zhou,et al ], appl. Surf. Sci.,2023, 613, 156004 ], and a scientific guiding idea is provided for the improvement of the mechanical property of the polybenzoxazine high-strength aerogel.
Besides the representative research cases, there are also active attacks that the polybenzoxazine high-strength aerogel is developed by a plurality of units at home and abroad, but the researches are developed around the theme of directly synthesizing different polybenzoxazine aerogels by different benzoxazine monomers, so that the comprehensive performance of the polybenzoxazine high-strength aerogel is difficult to be improved fundamentally, such as further improvement of strength, deformability, hydrophobic capability and the like. For this reason, research on the compounding of polybenzoxazine aerogel to further improve its comprehensive properties is becoming a strong need in the field of high strength aerogel.
Disclosure of Invention
The invention aims to solve the problems and provide a preparation method of the polybenzoxazine@cellulose nanofiber high-strength aerogel, which aims to further improve the strength, deformability and hydrophobicity of the polybenzoxazine aerogel on the basis of maintaining the thermal insulation performance.
In order to solve the technical problems, the technical scheme of the invention is as follows: the preparation method of the polybenzoxazine@cellulose nanofiber high-strength aerogel is characterized by comprising the following steps of:
s1, adding a benzoxazine monomer with a specific structure into a mixed solvent dispersion liquid of cellulose nanofiber, and stirring at a certain speed until the benzoxazine monomer is completely dissolved;
s2, after the hydrophobic modifier and the photocatalyst are added, promoting the benzoxazine monomer in the step S1 to be partially opened through photocatalysis induction so as to limit the cellulose nanofiber in a partially formed gel structure, and avoiding agglomeration caused by subsequent severe reaction;
s3, promoting the ring-opening polymerization reaction of the benzoxazine monomer to be complete through a hydrothermal-assisted sol-gel method;
s4, performing impurity removal and solvent replacement on the wet gel obtained in the step S3;
s5, placing the alcogel obtained in the step S4 into a protective solution to carry out supercritical CO 2 And (5) drying.
Further, the benzoxazine monomer with a specific structure in the step S1 is designated as a monomer 1, a monomer 2 or a combination of the two, and the stirring speed is 1200-2400 rpm.
Further, in the dispersion liquid composed of the cellulose nanofiber and the mixed solvent in the step S1, the cellulose nanofiber needs to be carboxylated, the cross section size is 4-70 nm, the fiber length is 2-10 μm, and the mixed solvent is a mixed solution composed of water and a strong polar organic reagent, and the volume ratio is 1:0.5 to 2 percent, and the mass fraction of the cellulose nano fiber is 4 to 36 percent.
Further, the ratio of the benzoxazine monomer to the dispersion in the step S1 is 1g: 4.2-10.6 ml.
Further, the mass ratio of the hydrophobic modifier in the step S2 to the benzoxazine monomer in the step S1 is 1:20 to 50, the mass ratio of the photocatalyst to the benzoxazine monomer in the step S1 is 1: 50-100, and the irradiation ultraviolet wavelength is 280-400 nm.
Further, the solvent for the hydrothermal reaction in the step S3 is N, N-dimethylformamide, aniline, methanol or ethylene glycol, the reaction time is 36-60 h, and the reaction temperature is 140-180 ℃.
Further, the temperature rising rate in the step S5 is 0.1-0.3 ℃ until reaching a supercritical state, and the standing time in the supercritical state is 2-5 h.
The beneficial effects of the invention are as follows:
1. the preparation method of the polybenzoxazine@cellulose nanofiber high-strength aerogel provided by the invention has the advantages that the cellulose nanofiber is used as a one-dimensional nanomaterial with ultrahigh strength, the strength is more than 5 times that of steel, but the density is only 1/5 of that of the steel, and the preparation method is very suitable for the composite reinforcement of the polybenzoxazine aerogel. The invention successfully realizes the core-shell type polybenzoxazine@cellulose with one-dimensional basic component by constructing the chemical crosslinking effect between the benzoxazine monomer and the specific carboxylated cellulose nanofiberNanofiber high strength aerogels. Because of the strength difference between cellulose nanofibers and polybenzoxazines, the aerogel, when broken, follows a special core-shell separation mechanism to generate a great deal of energy consumption, and macroscopically shows strength surge and deformation capability enhancement. At 0.175-0.327 g/cm 3 Based on the structure of low density and high porosity of 81.4-90.7%, the aerogel shows compressive strength of 23.4-82.5 MPa and fracture strain of 73.5-85.1%, and the comprehensive mechanical properties of the aerogel are far superior to those of the high-strength aerogel prepared in other reports. Meanwhile, the aerogel also has a low heat conductivity coefficient of 0.02913-0.04677W/(m.K), and has extremely high application value in the field of thermal insulation.
2. The polybenzoxazine@cellulose nanofiber high-strength aerogel prepared by utilizing the adsorption property difference has a nanoscale lotus leaf-like hydrophobic surface, the hydrophobic characteristic of the superhydrophobic material is generated, the hydrophobic angle is as high as 152.3-163.1 degrees, and the damage of water vapor to the aerogel structure in the actual use environment is avoided. In addition, the process flow of the invention is simpler, and the prepared composite aerogel combines excellent comprehensive mechanical property, thermal insulation property and hydrophobic property, has very broad application prospect, and is suitable for industrialized popularization and wide application in various fields.
Drawings
FIG. 1 is a schematic diagram showing the comparison of monomer 1 and monomer 2 in the preparation method of the polybenzoxazine@cellulose nanofiber high strength aerogel according to the invention;
FIG. 2 is an SEM image of an aerogel prepared according to one embodiment of the invention;
FIG. 3 is an SEM image of an aerogel prepared according to example II of the invention;
FIG. 4 is an SEM image of an aerogel prepared according to example III of the invention.
Detailed Description
The invention is further described with reference to the accompanying drawings and specific examples:
example 1
As shown in fig. 1 and fig. 2, the preparation method of the polybenzoxazine@cellulose nanofiber high strength aerogel provided by the invention comprises the following steps:
s1, adding a benzoxazine monomer with a specific structure into a mixed solvent dispersion liquid of cellulose nanofiber, and stirring at a certain speed until the benzoxazine monomer is completely dissolved.
The benzoxazine monomer with a specific structure in the step S1 is designated as a monomer 1, a monomer 2 or a combination of the two, and the stirring speed is 1200-2400 rpm. In a dispersion liquid composed of cellulose nano fibers and a mixed solvent, the cellulose nano fibers need to be carboxylated, the cross section size is 4-70 nm, the fiber length is 2-10 mu m, and the mixed solvent is a mixed solution composed of water and a strong polar organic reagent, and the volume ratio is 1:0.5 to 2 percent, and the mass fraction of the cellulose nano fiber is 4 to 36 percent. The ratio of benzoxazine monomer to dispersion was 1g: 4.2-10.6 ml.
In this example, 10g of monomer 1 was added to 80ml of 25wt.% carboxylated cellulose nanofiber mixed dispersion and stirred at 1500rpm to complete dissolution. Wherein the section size of the nanofiber is 30nm, the length is 5 mu m, the mixed solvent consists of water and dimethyl sulfoxide, and the volume ratio is 1:2.
s2, after the hydrophobic modifier and the photocatalyst are added, the benzoxazine monomer in the step S1 is promoted to be partially open by photocatalysis induction, so that the cellulose nanofiber is limited in a partially formed gel structure, and agglomeration caused by subsequent severe reaction is avoided.
The mass ratio of the hydrophobic modifier to the benzoxazine monomer in the step S1 is 1:20 to 50, the mass ratio of the photocatalyst to the benzoxazine monomer in the step S1 is 1: 50-100, and the irradiation ultraviolet wavelength is 280-400 nm.
In this example, 0.5g of the Hydrophobic modifier Hydrophobic-260 and 0.1g of the photocatalyst benzophenone were dissolved in the above sol system and irradiated under a 320nm ultraviolet lamp until the sol system was completely cured, to obtain an incompletely gelled polybenzoxazine@cellulose nanofiber gel.
S3, promoting the ring-opening polymerization reaction of the benzoxazine monomer to be complete by a hydrothermal-assisted sol-gel method.
The solvent for the hydrothermal reaction is N, N-dimethylformamide, aniline, methanol or glycol, the reaction time is 36-60 h, and the reaction temperature is 140-180 ℃.
In this example, the incompletely reacted gel in step S2 was added to a hydrothermal reaction kettle, methanol was added until the gel was submerged, and a hydrothermal-assisted sol-gel reaction was performed at 140 ℃ for 60 hours to obtain a completely reacted polybenzoxazine @ cellulose nanofiber wet gel.
S4, performing impurity removal and solvent replacement operation on the wet gel obtained in the step S3.
Adopting N, N-dimethylformamide with the volume 10 times of that of the gel to carry out impurity removal treatment on the gel obtained in the step 3, wherein the single impurity removal time is 8h, and the total impurity removal time is 3 times; the gel was then subjected to a solvent displacement operation with 10 volumes of ethanol, a single displacement time of 12h, a total of 3 displacements.
S5, placing the alcogel obtained in the step S4 into a protective solution to carry out supercritical CO 2 And (5) drying.
The temperature rising rate is 0.1-0.3 ℃, the temperature reaches a supercritical state, and the standing time in the supercritical state is 2-5 h.
After reaching a drying temperature of 50 ℃ at a heating rate of 0.3 ℃/min, adjusting the drying pressure to 12MPa, and carrying out supercritical CO for 10 hours on the alcogel obtained in the step 4 after standing for 3 hours 2 And (5) drying to obtain the polybenzoxazine@cellulose nanofiber aerogel.
In this example, SEM images of the prepared polybenzoxazine @ cellulose nanofiber aerogel are shown in fig. 2. The aerogel was at 0.215g/cm 3 The structure with low density and 89.2% high porosity has high compression strength of 36.7MPa, high fracture strain of 80.1%, low heat conductivity of 0.02913W/(m.K) and superhigh hydrophobic angle of 161.3 degrees.
In fig. 1 of the present invention, (a) is a schematic structural diagram of a monomer 1, and (b) is a schematic structural diagram of a monomer 2.
The method comprises the steps of firstly dissolving benzoxazine monomer with a specific structure into mixed solvent dispersion liquid of cellulose nanofiber, carrying out photocatalytic reaction to partially open the ring after the monomer is dissolved, and carrying out hydrothermal assistanceThe sol-gel process of the (2) enables the ring opening to be complete, and the wet gel of the polybenzoxazine@cellulose nanofiber is obtained. Subsequently, through impurity removal, solvent replacement and supercritical CO 2 And drying to obtain the polybenzoxazine@cellulose nanofiber aerogel.
Example two
This embodiment differs from the first embodiment in the following points:
s1, 10g of monomer 2 was added to 65ml of 20wt.% carboxylated cellulose nanofiber mixed dispersion and stirred at 1800rpm until completely dissolved. Wherein the section size of the nanofiber is 20nm, the length is 10 mu m, the mixed solvent consists of water and N-methyl pyrrolidone, and the volume ratio is 1:1.
s2, the conditions are the same as those of the first example except that the mass of the hydrophobic modifier is 0.3g, the mass of the photocatalyst is 0.1g, and the wavelength of ultraviolet light is 400nm.
S3, the conditions are the same as those of the first example except that aniline is added, and the reaction temperature and the reaction time are 180 ℃ and 36 hours respectively.
S4, the content of the step S4 is the same as that of the first embodiment.
S5, the conditions are the same as those of the first example except that the heating rate is 0.1 ℃/min and the standing time is 2 hours.
Example two SEM images of the prepared polybenzoxazine @ cellulose nanofiber aerogel are shown in figure 3. The aerogel is 0.254g/cm 3 The structure with low density and 85.8% high porosity has high compression strength of 45.3MPa, high breaking strain of 83.3%, low heat conductivity of 0.03389W/(m.K) and superhigh hydrophobic angle of 162.2 degrees.
This embodiment is identical to embodiment one except for the differences described above.
Example III
This embodiment differs from embodiment one in the following parts:
s1, 5g of monomer 1 and 5g of monomer 2 were added to 60ml of 10wt.% carboxylated cellulose nanofiber mixed dispersion and stirred at 2400rpm until completely dissolved. Wherein the section size of the nanofiber is 4nm, the length is 3 mu m, the mixed solvent consists of water and N, N-dimethylformamide, and the volume ratio is 1:0.5.
s2, the conditions are the same as those of the first example except that the mass of the hydrophobic modifier is 0.2g, the mass of the photocatalyst is 0.2g, and the wavelength of ultraviolet light is 280 nm.
S3, the conditions are the same as those of the first example except that ethylene glycol is added, and the reaction temperature and the reaction time are 160 ℃ and 54h respectively.
S4, the content of the step S4 is the same as that of the first embodiment.
S5, the conditions are the same as those of the first example except that the temperature rising rate is 0.2 ℃/min and the standing time is 5 hours.
Example three SEM images of the prepared polybenzoxazine @ cellulose nanofiber aerogel are shown in figure 4. The aerogel was at 0.247g/cm 3 The structure with low density and 87.2% high porosity has high compression strength of 69.4MPa, high fracture strain of 73.5%, low heat conductivity of 0.03122W/(m.K) and superhigh hydrophobic angle of 160.7 degrees.
This embodiment is identical to embodiment one except for the differences described above.
Example IV
This embodiment differs from embodiment one in the following parts:
s1, 8g of monomer 1 and 2g of monomer 2 were added to 42ml of 36wt.% carboxylated cellulose nanofiber mixed dispersion and stirred at 1200rpm until completely dissolved. Wherein the section size of the nanofiber is 70nm, the length is 10 mu m, the mixed solvent consists of water and N, N-dimethylformamide, and the volume ratio is 1:1.5.
s2, the conditions are the same as those of the first example except that the mass of the hydrophobic modifier is 0.3g, the mass of the photocatalyst is 0.15g, and the wavelength of ultraviolet light is 350 nm.
S3, the conditions are the same as those of the first example except that N, N-dimethylformamide is added, and the reaction temperature and the reaction time are 150 ℃ and 60 hours respectively.
S4, the content of the step S4 is the same as that of the first embodiment.
S5, the conditions are the same as those of the first example except that the heating rate is 0.1 ℃/min and the standing time is 4 hours.
Example four prepared polybenzoxazine@cellulose nanofiber aerogel at 0.327g/cm 3 The structure with low density and 81.4% high porosity has high compression strength of 82.5MPa, high breaking strain of 84.3%, low heat conductivity of 0.04677W/(m.K) and superhigh hydrophobic angle of 162.2 degrees.
This embodiment is identical to embodiment one except for the differences described above.
Example five
This embodiment differs from embodiment one in the following parts:
s1, 10g of monomer 2 was added to 106ml of 4wt.% carboxylated cellulose nanofiber mixed dispersion and stirred at 1500rpm until completely dissolved. Wherein the section size of the nanofiber is 4nm, the length is 2 mu m, the mixed solvent consists of water and dimethyl sulfoxide, and the volume ratio is 1:2.
s2, the conditions were the same as in example one except that the mass of the hydrophobic modifier was 0.5g, the mass of the photocatalyst was 0.1g, and the wavelength of ultraviolet light was 310 nm.
S3, the conditions are the same as those of the first example except that methanol is added, and the reaction temperature and the reaction time are 170 ℃ and 40 hours respectively.
S4, the content of the step S4 is the same as that of the first embodiment.
S5, the conditions are the same as those of the first example except that the temperature rising rate is 0.3 ℃/min and the standing time is 5 hours.
Example five prepared polybenzoxazine@cellulose nanofiber aerogel at 0.175g/cm 3 The structure with low density and high porosity of 90.7 percent has high compression strength of 23.6MPa, high fracture strain of 74.2 percent, low heat conductivity coefficient of 0.03528W/(m.K) and superhigh hydrophobic angle of 152.3 degrees.
This embodiment is identical to embodiment one except for the differences described above.
Example six
This embodiment differs from embodiment one in the following parts:
s1, 3g of monomer 1 and 7g of monomer 2 were added to 80ml of 25wt.% carboxylated cellulose nanofiber mixed dispersion and stirred at 1600rpm to complete dissolution. Wherein the section size of the nanofiber is 10nm, the length is 6 mu m, the mixed solvent consists of water and N, N-dimethylformamide, and the volume ratio is 1:0.5.
s2, the conditions are the same as those of the first example except that the mass of the hydrophobic modifier is 0.4g, the mass of the photocatalyst is 0.2g, and the wavelength of ultraviolet light is 380 nm.
S3, the other conditions are the same as those of the first example except that aniline is added, and the reaction temperature and the reaction time are 150 ℃ and 54 hours respectively;
s4, the content of the step S4 is the same as that of the first embodiment.
S5, the conditions are the same as those of the first example except that the heating rate is 0.2 ℃/min and the standing time is 2 h.
Example six prepared polybenzoxazine @ cellulose nanofiber aerogel at 0.227g/cm 3 The structure with low density and 89.0% high porosity has high compression strength of 38.5MPa, high breaking strain of 81.8%, low heat conductivity of 0.03034W/(m.K) and superhigh hydrophobic angle of 162.9 degrees.
This embodiment is identical to embodiment one except for the differences described above.
Example seven
This embodiment differs from embodiment one in the following parts:
step 1: 10g of monomer 1 was added to 75ml of 36wt.% carboxylated cellulose nanofiber mixed dispersion and stirred at 2000rpm to complete dissolution. Wherein the section size of the nanofiber is 30nm, the length is 2 mu m, the mixed solvent consists of water and dimethyl sulfoxide, and the volume ratio is 1:2.
step 2: the conditions were the same as in example one except that the mass of the hydrophobic modifier was 0.3g, the mass of the photocatalyst was 0.1g, and the wavelength of ultraviolet light was 300 nm.
Step 3: the conditions were the same as in example one except that methanol was added and the reaction temperature and duration were 140℃and 60 hours, respectively.
Step 4: the same as in step S4 of the first embodiment.
Step 5: the conditions were the same as in example one except that the temperature rising rate was 0.1℃per minute and the standing time was 4 hours.
Example seven prepared polybenzoxazine@cellulose nanofiber aerogel at 0.248g/cm 3 The structure with low density and 88.3% high porosity has high compression strength of 44.2MPa, high breaking strain of 82.1%, low heat conductivity coefficient of 0.03125W/(m.K) and superhigh hydrophobic angle of 161.7 degrees.
This embodiment is identical to embodiment one except for the differences described above.
Example eight
This embodiment differs from embodiment one in the following parts:
s1, 2g of monomer 1 and 8g of monomer 2 were added to 90ml of 16wt.% carboxylated cellulose nanofiber mixed dispersion and stirred at 2200rpm until completely dissolved. Wherein the section size of the nanofiber is 40nm, the length is 5 mu m, the mixed solvent consists of water and N, N-dimethylformamide, and the volume ratio is 1:0.5.
s2, the conditions are the same as those of the first example except that the mass of the hydrophobic modifier is 0.5g, the mass of the photocatalyst is 0.15g, and the wavelength of ultraviolet light is 400nm.
S3, the conditions are the same as those of the first example except that aniline is added, and the reaction temperature and the reaction time are 160 ℃ and 45h respectively.
S4, the content of the step S4 is the same as that of the first embodiment.
S5, the conditions are the same as those of the first example except that the heating rate is 0.3 ℃/min and the standing time is 2 hours.
Example eight prepared polybenzoxazine @ cellulose nanofiber aerogel at 0.212g/cm 3 The structure with low density and 89.7% high porosity has high compression strength of 34.4MPa, high fracture strain of 78.6%, low heat conductivity of 0.03056W/(m.K) and superhigh hydrophobic angle of 160.4 degrees.
This embodiment is identical to embodiment one except for the differences described above.
Example nine
This embodiment differs from embodiment one in the following parts:
s1, 10g of monomer 1 was added to 50ml of a 24wt.% carboxylated cellulose nanofiber mixed dispersion and stirred at 1500rpm until completely dissolved. Wherein the section size of the nanofiber is 50nm, the length is 8 mu m, the mixed solvent consists of water and N-methyl pyrrolidone, and the volume ratio is 1:2.
s2, the conditions are the same as those of the first example except that the mass of the hydrophobic modifier is 0.4g, the mass of the photocatalyst is 0.2g, and the wavelength of ultraviolet light is 280 nm.
S3, the conditions are the same as those of the first example except that methanol is added, and the reaction temperature and the reaction time are 150 ℃ and 50 hours respectively.
S4, the content of the step S4 is the same as that of the first embodiment.
S5, the conditions are the same as those of the first example except that the heating rate is 0.1 ℃/min and the standing time is 4 hours.
The polybenzoxazine@cellulose nanofiber aerogel prepared in example 9 was at 0.275g/cm 3 The structure with low density and 84.3% high porosity has high compression strength of 62.4MPa, high breaking strain of 85.1%, low heat conductivity of 0.03905W/(m.K) and superhigh hydrophobic angle of 163.1 degrees.
This embodiment is identical to embodiment one except for the differences described above.
Examples ten
This embodiment differs from embodiment one in the following parts:
s1, 10g of monomer 1 was added to 100ml of 36wt.% carboxylated cellulose nanofiber mixed dispersion and stirred at 2100rpm until completely dissolved. Wherein the section size of the nanofiber is 20nm, the length is 5 mu m, the mixed solvent consists of water and N-methyl pyrrolidone, and the volume ratio is 1:0.5.
s2, the conditions are the same as those of the first example except that the mass of the hydrophobic modifier is 0.2g, the mass of the photocatalyst is 0.2g, and the wavelength of ultraviolet light is 380 nm.
S3, the conditions are the same as those of the first example except that ethylene glycol is added, and the reaction temperature and the reaction time are 140 ℃ and 60 hours respectively.
S4, the content of the step S4 is the same as that of the first embodiment.
S5, the other conditions are the same as those of the first example except that the heating rate is 0.3 ℃/min and the standing time is 5 hours.
The polybenzoxazine@cellulose nanofiber aerogel prepared in example 10 was at 0.198g/cm 3 The structure with low density and 89.6% high porosity has high compression strength of 23.4MPa, high fracture strain of 79.3%, low heat conductivity of 0.03211W/(m.K) and superhigh hydrophobic angle of 158.7 degrees.
This embodiment is identical to embodiment one except for the differences described above.
Those of ordinary skill in the art will recognize that the embodiments described herein are for the purpose of aiding the reader in understanding the principles of the present invention and should be understood that the scope of the invention is not limited to such specific statements and embodiments. Those of ordinary skill in the art can make various other specific modifications and combinations from the teachings of the present disclosure without departing from the spirit thereof, and such modifications and combinations remain within the scope of the present disclosure.
Claims (7)
1. The preparation method of the polybenzoxazine@cellulose nanofiber high-strength aerogel is characterized by comprising the following steps of:
s1, adding a benzoxazine monomer with a specific structure into a mixed solvent dispersion liquid of cellulose nanofiber, and stirring at a certain speed until the benzoxazine monomer is completely dissolved;
s2, after the hydrophobic modifier and the photocatalyst are added, promoting the benzoxazine monomer in the step S1 to be partially opened through photocatalysis induction so as to limit the cellulose nanofiber in a partially formed gel structure, and avoiding agglomeration caused by subsequent severe reaction;
s3, promoting the ring-opening polymerization reaction of the benzoxazine monomer to be complete through a hydrothermal-assisted sol-gel method;
s4, performing impurity removal and solvent replacement on the wet gel obtained in the step S3;
s5, placing the alcogel obtained in the step S4 into a protective solution to carry out supercritical CO 2 And (5) drying.
2. The method for preparing the polybenzoxazine@cellulose nanofiber high strength aerogel according to claim 1, wherein the method comprises the following steps: the benzoxazine monomer with a specific structure in the step S1 is designated as a monomer 1, a monomer 2 or a combination of the two, and the stirring speed is 1200-2400 rpm.
3. The method for preparing the polybenzoxazine@cellulose nanofiber high strength aerogel according to claim 1, wherein the method comprises the following steps: in the dispersion liquid formed by the cellulose nanofiber and the mixed solvent in the step S1, the cellulose nanofiber is subjected to carboxylation treatment, the cross section size is 4-70 nm, the fiber length is 2-10 mu m, and the mixed solvent is a mixed solution formed by water and a strong polar organic reagent, wherein the volume ratio is 1:0.5 to 2 percent, and the mass fraction of the cellulose nano fiber is 4 to 36 percent.
4. The method for preparing the polybenzoxazine@cellulose nanofiber high strength aerogel according to claim 1, wherein the method comprises the following steps: the ratio of benzoxazine monomer to dispersion in step S1 is 1g: 4.2-10.6 ml.
5. The method for preparing the polybenzoxazine@cellulose nanofiber high strength aerogel according to claim 1, wherein the method comprises the following steps: the mass ratio of the hydrophobic modifier in the step S2 to the benzoxazine monomer in the step S1 is 1:20 to 50, the mass ratio of the photocatalyst to the benzoxazine monomer in the step S1 is 1: 50-100, and the irradiation ultraviolet wavelength is 280-400 nm.
6. The method for preparing the polybenzoxazine@cellulose nanofiber high strength aerogel according to claim 1, wherein the method comprises the following steps: the solvent for the hydrothermal reaction in the step S3 is N, N-dimethylformamide, aniline, methanol or ethylene glycol, the reaction time is 36-60 h, and the reaction temperature is 140-180 ℃.
7. The method for preparing the polybenzoxazine@cellulose nanofiber high strength aerogel according to claim 1, wherein the method comprises the following steps: the temperature rising rate in the step S5 is 0.1-0.3 ℃ until reaching a supercritical state, and the standing time in the supercritical state is 2-5 h.
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN117247654A (en) * | 2023-11-17 | 2023-12-19 | 西南石油大学 | Water-soluble benzoxazine and inorganic fiber composite aerogel and preparation method thereof |
| CN118222248A (en) * | 2024-05-24 | 2024-06-21 | 西南石油大学 | Flame-retardant barrier type benzoxazine and cellulose composite aerogel phase-change material and preparation method thereof |
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Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN117247654A (en) * | 2023-11-17 | 2023-12-19 | 西南石油大学 | Water-soluble benzoxazine and inorganic fiber composite aerogel and preparation method thereof |
| CN117247654B (en) * | 2023-11-17 | 2024-02-09 | 西南石油大学 | Water-soluble benzoxazine and inorganic fiber composite aerogel and preparation method thereof |
| CN118222248A (en) * | 2024-05-24 | 2024-06-21 | 西南石油大学 | Flame-retardant barrier type benzoxazine and cellulose composite aerogel phase-change material and preparation method thereof |
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