CN112662015A - Flame-retardant nano-cellulose composite aerogel with oriented structure and preparation method thereof - Google Patents
Flame-retardant nano-cellulose composite aerogel with oriented structure and preparation method thereof Download PDFInfo
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Abstract
The invention provides a flame-retardant nano-cellulose composite aerogel with an oriented structure and a preparation method thereof, wherein the preparation method comprises the following steps: s1, mixing the nano-cellulose suspension with siloxane hydrolysate, and crosslinking through water-soluble metal salt to obtain the composite nano-cellulose hydrogel; s2, carrying out solution replacement on the composite nano-cellulose hydrogel in an alcoholic solution containing a carbonizing agent to obtain an alcoholic gel containing the carbonizing agent; the carbonizing agent is preferably p-toluenesulfonic acid; s3, directionally freezing the alcogel containing the carbonizing agent to obtain the flame-retardant nano cellulose composite aerogel with a directional structure. According to the invention, the addition of the carbonizing agents such as methyl benzene sulfonic acid in the preparation process improves the carbonization degree of cellulose, and blocks the transfer of heat and combustible volatile components; meanwhile, siloxane is introduced in situ during preparation, so that the flame retardant effect is further achieved. The nano-cellulose composite aerogel disclosed by the invention is low in heat conductivity coefficient and excellent in heat preservation and heat insulation performance.
Description
Technical Field
The invention relates to the technical field of heat insulation materials, in particular to a flame-retardant nano cellulose composite aerogel with an oriented structure and a preparation method thereof.
Background
Aerogel, one of the lightest solid materials in the world, is known as "the peculiar material of the 21 st century" because of its porous structure, and has excellent characteristics of high porosity, large specific surface area, low bulk density, and the like. The porous structure of the aerogel enables the aerogel to have extremely low heat conductivity coefficient, so the aerogel has huge application prospect in the field of heat preservation and insulation.
Aerogels are of many types and can be classified into oxide aerogels, carbide aerogels, and polymer-based organic aerogels. The traditional carbide aerogel is generally made of non-renewable and non-biodegradable materials such as carbon nanotubes and graphene, but the aerogel made of natural renewable biomass resources has obvious advantages in consideration of the requirements of environment, green and sustainable development. With the increasing shortage of resources, cellulose has a great application prospect as a renewable resource widely distributed in plants, and the renewable environment-friendly material is widely applied to the fields of paper making, biomedicine, supercapacitors, adsorption and the like due to biodegradability, nontoxicity and biocompatibility. The cellulose aerogel prepared by using cellulose has the characteristics of high porosity, extremely low density, low heat conductivity coefficient and the like, and the mechanical property of the cellulose aerogel is obviously superior to that of inorganic aerogel due to a special cross-linking structure formed by the action of hydrogen bonds among high molecular chains. Therefore, the cellulose aerogel is suitable for being applied to the field of heat preservation and heat insulation.
As can be seen from the literature, cellulose aerogels have been studied extensively. Cyrielle et al prepared nanocellulose from pectin and dried with supercritical carbon dioxide to prepare a Biomass cellulose Aerogel material (Rudaz C, Courson R, Bonnet L, et al. Aeronectin: full Biomass-Based mechanical Strong and Thermal Superinsulating Aerogel [ J ]. Biomacromolecules 2014,15(6): 2188.). However, pure cellulose aerogels are extremely flammable due to the inherent flammability of cellulose, greatly limiting their widespread use in the field of thermal insulation. In order to improve the flame retardancy of cellulose aerogel, some researches have added inorganic materials to cellulose aerogel systems. Chinese patent publication No. CN 111440353a discloses a method for preparing a hydrophobic flame-retardant cellulose aerogel, which mainly improves flame retardancy by adding boron nitride, montmorillonite, and synergistic effect of organosilane and fluoride. However, the thermal conductivity of the aerogel prepared by the method is greatly improved, resulting in rapid reduction of thermal insulation performance. Therefore, the preparation of the cellulose aerogel which is safe, environment-friendly, heat-insulating and flame-retardant is very important.
Disclosure of Invention
In view of this, the present application provides a flame-retardant nanocellulose composite aerogel with an oriented structure and a preparation method thereof, and the nanocellulose composite aerogel prepared by the present invention has good flame retardancy, and simultaneously has excellent heat insulation performance, and can be used as a thermal insulation material.
The invention provides a preparation method of a flame-retardant nano-cellulose composite aerogel with an oriented structure, which comprises the following steps:
s1, mixing the nano-cellulose suspension with siloxane hydrolysate, and crosslinking through water-soluble metal salt to obtain the composite nano-cellulose hydrogel;
s2, carrying out solution replacement on the composite nano-cellulose hydrogel in an alcoholic solution containing a carbonizing agent to obtain an alcoholic gel containing the carbonizing agent; the carbonizing agent is selected from one or more of p-toluenesulfonic acid, diphenyl phosphonic acid and trifluoromethanesulfonic acid;
s3, directionally freezing the alcogel containing the carbonizing agent to obtain the flame-retardant nano cellulose composite aerogel with a directional structure.
Preferably, the siloxane hydrolysate is a solution obtained by hydrolyzing siloxane under acidic conditions, and the siloxane is one or more selected from methyltrimethoxysilane and methyltriethoxysilane.
Preferably, the nanocellulose suspension is prepared according to the following steps: in an alkaline environment, mixing cellulose raw pulp with tetramethyl piperidine nitrogen oxide, bromide, hypochlorite and water for reaction, and then carrying out mechanical treatment to obtain the nano cellulose suspension.
Preferably, when the nano-cellulose suspension is prepared, the cellulose raw pulp is derived from one or more of eucalyptus, poplar and straw; the bromide is selected from one or more of sodium bromide, potassium bromide and iodine bromide; the mass ratio of the cellulose raw pulp to the tetramethylpiperidine nitrogen oxide to the bromide to the water is 1: 0.01-0.02: 0.05-0.1: 50.
preferably, in the step S1, the mass ratio of the nano-cellulose suspension to the siloxane hydrolysate is 1:0.1 to 1.
Preferably, the step S1 is carried out under the condition of stirring, and the stirring speed is 1000-1200 r/min; and adding a calcium chloride solution for crosslinking to obtain the composite nano cellulose hydrogel.
Preferably, in the step S2, the alcohol solution containing the carbonizing agent is an ethanol solution containing 5 to 10 wt% of p-toluenesulfonic acid.
Preferably, in the step S2, the ethanol solution of p-toluenesulfonic acid is replaced at intervals of 6 to 10 hours, and the replacement time is not less than 24 hours.
Preferably, in step S3, liquid nitrogen is selected for freeze drying during the directional freezing; the temperature of freeze drying is 20-30 ℃; the freeze drying time is 24-36 h; the vacuum pressure for freeze drying is lower than 20 Pa.
The invention provides the flame-retardant nano-cellulose composite aerogel obtained by the preparation method, which shows a layered structure on the cross section and has disordered cellular holes on the longitudinal section.
General cellulose aerogel is inflammable, and under certain heat radiation, the phenomenon of lighting will take place within a few seconds, and this makes general cellulose aerogel be used for thermal-insulated field to have huge potential safety hazard.
Compared with the traditional nano-cellulose material, the nano-cellulose composite aerogel material prepared by the method provided by the invention has the following obvious advantages: according to the invention, the addition of the carbonizing agents such as methyl benzene sulfonic acid in the preparation process improves the carbonization degree of cellulose, and blocks the transfer of heat and combustible volatile components; meanwhile, siloxane is introduced in situ in the preparation process, and a silicon dioxide layer is uniformly introduced on the surface of the cellulose, so that oxygen and combustible volatile components are further blocked, and the flame retardant effect is achieved. In addition, the obtained nano-cellulose composite aerogel has low heat conductivity coefficient and excellent heat preservation and insulation performance. The experimental results show that: the cellulose aerogel obtained by the invention has the limiting oxygen index of 51 percent and the thermal conductivity coefficient of 0.027W/m.K.
In addition, the invention finally adopts a directional freezing mode, so that the material has a directional structure, namely, the cross section of the material shows a layered structure, the longitudinal section of the material is a disordered cellular hole structure, and the specific directional structure improves the mechanical property of the aerogel. The Young modulus of the cellulose aerogel obtained by freeze drying is only 0.0694MPa, and after the directional freezing strategy is adopted, the Young modulus of the aerogel is improved to 3.657MPa, which is improved by nearly 52 times. The nano-cellulose composite material provided by the invention is simple in preparation process, simple and convenient to operate, and suitable for mass production and popularization and use.
Drawings
Fig. 1 is a schematic view of a process for preparing a flame-retardant nanocellulose composite aerogel having an oriented structure according to an embodiment of the present invention;
FIG. 2 is a physical diagram of a nanocomposite cellulose aerogel prepared in example 1;
FIG. 3 is a scanning electron microscope image of the nanocomposite cellulose aerogel prepared in example 1 and the pure cellulose aerogel prepared in comparative example 1;
FIG. 4 is a thermogravimetric plot of the nanocomposite cellulose aerogels prepared in examples 1-3 and the nanocellulose aerogel prepared in comparative example 1;
FIG. 5 is a comparison graph of the residual real estate of the sample after cone calorimetry tests for the nanocomposite cellulose aerogels prepared in examples 1-3 and the nanocellulose aerogel prepared in comparative example 1;
FIG. 6 is a realistic comparison of the combustion process of the nanocomposite cellulose aerogel prepared in example 3 and the nanocellulose aerogel prepared in comparative example 1 in the cone calorimetry test;
FIG. 7 is a histogram of the ignition time of the nanocomposite cellulose aerogels prepared in examples 1-3 and the nanocellulose aerogel prepared in comparative example 1 in the cone calorimetry test;
fig. 8 is a graph showing the total smoke emission of the nanocomposite cellulose aerogels prepared in examples 1 to 3 and the nanocellulose aerogel prepared in comparative example 1.
Detailed Description
The technical solutions in the embodiments of the present invention are clearly and completely described below, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
The invention provides a preparation method of a flame-retardant nano-cellulose composite aerogel with an oriented structure, which comprises the following steps:
s1, mixing the nano-cellulose suspension with siloxane hydrolysate, and crosslinking through water-soluble metal salt to obtain the composite nano-cellulose hydrogel;
s2, carrying out solution replacement on the composite nano-cellulose hydrogel in an alcoholic solution containing a carbonizing agent to obtain an alcoholic gel containing the carbonizing agent; the carbonizing agent is selected from one or more of p-toluenesulfonic acid, diphenyl phosphonic acid and trifluoromethanesulfonic acid;
s3, directionally freezing the alcogel containing the carbonizing agent to obtain the flame-retardant nano cellulose composite aerogel with a directional structure.
The nano-cellulose composite aerogel prepared by the method has good flame retardant property, the limiting oxygen index reaches 51%, the nano-cellulose composite aerogel can not be continuously combusted in an air environment, can be self-extinguished when leaving a fire source, has excellent heat insulation property and mechanical property, and can be used as a heat insulation material. The method for preparing the nano-cellulose composite aerogel is simple, and the material is safe and environment-friendly.
Referring to fig. 1, fig. 1 is a schematic view of a process for preparing a flame-retardant nanocellulose composite aerogel having an oriented structure according to an embodiment of the present invention. The embodiment of the invention firstly prepares the nano-cellulose suspension: taking cellulose protoplasm (softwood pulp), mixing and reacting with tetramethylpiperidine nitrogen oxide (Tempo), bromide, hypochlorite and water in an alkaline environment, and mechanically treating to obtain nano cellulose suspension (containing nano fibrillated cellulose NFC).
In some embodiments of the invention, in an alkaline environment, mixing cellulose raw pulp, tetramethylpiperidine oxynitride, bromide, sodium hypochlorite and deionized water, stirring and reacting for 4-8 hours, then mechanically treating the obtained mixture by using a household stirrer, and then washing with deionized water to obtain a nano-cellulose suspension. Wherein the cellulose raw pulp is derived from eucalyptus, poplar and straw to obtain the nano fibrous raw material. The alkaline environment is to keep the pH value of the system to be 10-10.5 in the reaction process, and the alkaline environment can be realized by dropwise adding a sodium hydroxide solution in the reaction period. The hypochlorite mainly provides active chlorine, and preferably the mass content of the active chlorine in the sodium hypochlorite is 6-15%, and more preferably 10-15%. The bromide is preferably one or more of Sodium bromide (Sodium bromide), potassium bromide and iodine bromide; the water used may be deionized water. And the mass ratio of the cellulose raw pulp, the tetramethylpiperidine oxynitride, the bromide and the deionized water is preferably 1: 0.01-0.02: 0.05-0.1: 50. in the mechanical treatment, the stirring speed is preferably 1000-1200 r/min; the stirring time may be 30 minutes.
After obtaining the nano-cellulose suspension, the nano-cellulose suspension is rapidly stirred and mixed with the siloxane hydrolysate in a household stirrer, and then calcium chloride (CaCl) is added2) Solution to obtainNanocellulose hydrogel (also called hybrid hydrogel, composite nanocellulose hydrogel) compounded with a silicon component. The siloxane hydrolysate is a solution of siloxane hydrolyzed under acidic conditions (such as pH 3), the siloxane can be one or more selected from methyltrimethoxysilane and methyltriethoxysilane, and is preferably methyltrimethoxysilane (MTMS).
In a preferred embodiment of the present invention, the mass ratio of the nano-cellulose suspension to the siloxane hydrolysate (such as methyl trimethoxysilane hydrolysate, containing MTMS oligomers) is 1:0.1 to 1, preferably 1:0.1 to 0.6. According to the invention, calcium chloride is preferably used as a water-soluble metal salt to realize crosslinking, and the calcium chloride solution is a saline solution with the mass fraction of 5-10% of calcium chloride. In addition, the stirring speed can be 1000-1200 r/min, and the stirring time is preferably 10 minutes.
The method comprises the following steps of carrying out solution replacement on the obtained hydrogel in an alcoholic solution containing a carbonizing agent to obtain the alcoholic gel containing the carbonizing agent; the carbonizing agent is selected from one or more of p-toluenesulfonic acid, diphenyl phosphonic acid and trifluoromethanesulfonic acid, and is preferably p-toluenesulfonic acid (TsOH). Preferably, the alcohol solution containing the carbonizing agent is an ethanol solution containing p-toluenesulfonic acid, and more preferably an ethanol solution with the mass fraction of the p-toluenesulfonic acid being 5-10%.
In the embodiment of the invention, the obtained composite nano cellulose gel is subjected to solution replacement in an ethanol solution containing p-toluenesulfonic acid, the waste liquid is poured out at intervals of 6-10 hours, preferably at intervals of 8 hours, the ethanol solution of the p-toluenesulfonic acid is replaced, the replacement time is not less than 24 hours, preferably 24 hours, and the alcohol gel containing the p-toluenesulfonic acid is obtained.
In the embodiment of the invention, the alcogel is placed on a directional freezing device for directional freezing, so that the flame-retardant nano cellulose composite aerogel with a directional structure is obtained. Freeze drying, also known as sublimation drying, is a drying method in which a material is generally frozen below the freezing point of water, placed in a high vacuum (10-40 Pa) container, and heated to sublimate the water in the material directly from solid ice into water vapor. Liquid nitrogen (Liquid N) is preferably used for directional freezing in the invention2) Freeze-drying is carried out, firstly, the ice crystals formed by the solvent in the alcogel grow along a single direction, and then the ice crystals of the solvent are directly sublimated through freeze-drying. In the embodiment of the present invention, there is no particular limitation on the process of the directional freezing; wherein the temperature of freeze drying can be 20-30 ℃; the freeze drying time is 24-36 h; the vacuum pressure for freeze drying is lower than 20 Pa.
The embodiment of the invention provides the flame-retardant nano cellulose composite aerogel (for short, cellulose aerogel, nano composite cellulose aerogel and the like) obtained by the preparation method, which has an oriented structure, namely, a layered structure is shown on the cross section, and disordered honeycomb-shaped holes are formed on the longitudinal section.
The cellulose aerogel obtained by the invention has the characteristics of high porosity, large specific surface area and low volume density, and the specific directional structure also improves the mechanical properties of the aerogel; in addition, the limiting oxygen index can reach 51%, the heat conductivity coefficient can be 0.027W/m.K, and the Young modulus can reach 3.657 MPa. The nano-cellulose composite aerogel disclosed by the invention has the advantages of lower heat conductivity coefficient, excellent flame retardant property and excellent mechanical property, and can be used as a heat-insulating material.
In addition, the preparation process of the nano-cellulose composite material provided by the invention is simple and convenient to operate.
In order to further understand the present application, the following specifically describes the flame retardant nanocellulose composite aerogel with oriented structure and the preparation method thereof provided by the present application with reference to the examples. It should be understood, however, that these examples are for illustrative purposes only and are not intended to limit the scope of the present invention, which is defined by the following examples.
The examples, where specific techniques or conditions are not indicated, are to be construed according to the techniques or conditions described in the literature in the art or according to the product specifications. The reagents or instruments used are not indicated by manufacturers, and are all conventional products available on the market.
Example 1
Taking 1g of cellulose protoplasm, 0.015g of tetramethylpiperidine nitrogen oxide, 0.06g of sodium bromide and 100mL of deionized water in a beaker, mixing and stirring uniformly, adding 6mL of sodium hypochlorite solution with the mass fraction of 10%, and continuously stirring and reacting for 5 hours; during the reaction, the pH of the system was kept constant at 10.5 by dropwise addition of 0.5mol/L sodium hydroxide solution. Subsequently, the resulting mixture was mechanically treated with a household mixer at a rotation speed of 1000r/min, and after 30 minutes was washed with deionized water to obtain a nanocellulose suspension.
The resulting nanocellulose suspension was mixed with methyltrimethoxysilane hydrolysate obtained at pH 3, according to a 1:0.1, stirring and mixing for 10 minutes in a household stirrer at the rotating speed of 1200r/min, and then slowly dropwise adding a 10% calcium chloride solution to obtain the composite nano cellulose hydrogel.
And (3) carrying out solution replacement on the obtained composite nano-cellulose hydrogel in an ethanol solution containing 10% by mass of p-toluenesulfonic acid, pouring the waste liquid every 8 hours, replacing the ethanol solution of the p-toluenesulfonic acid, and replacing for 24 hours to obtain the alcoholic gel containing the p-toluenesulfonic acid.
Placing the alcogel on a directional freezing device shown in figure 1, performing directional freezing for 3h by using liquid nitrogen, and then performing freeze drying in a freeze dryer for 48 h to obtain the nano-cellulose composite aerogel material, wherein a physical diagram is shown in figure 2.
The nano-cellulose composite aerogel obtained in example 1 has a thermal conductivity of 0.027W/mK and excellent thermal insulation performance. FIG. 3 is a scanning electron microscope image of the nanocomposite cellulose aerogel prepared in example 1 and the pure cellulose aerogel prepared in comparative example 1; as can be seen from fig. 3, the nanocellulose composite aerogel obtained in example 1 has an oriented structure, in particular, a layered structure with a distinct cross-section, because of the strategy of directional freezing. FIG. 4 is a thermogravimetric plot with test conditions ranging from 30 ℃ to 800 ℃ at a temperature rate of 10 ℃/min; the abscissa is temperature and the ordinate is mass; as can be seen from fig. 4, the thermogravimetric residual amount of the nanocellulose aerogel obtained in example 1 is 35%, which is significantly higher than that of the pure cellulose aerogel. According to the limit oxygen index experiment, the limit oxygen index value of the nano-cellulose aerogel obtained in example 1 is 43.4%, which indicates that the aerogel has excellent flame retardant property.
In addition, as can be seen from fig. 5, the integrity of the sample graph of the nanocellulose composite aerogel obtained in example 1 after cone calorimetry test is good, and a layer of carbon black is formed on the surface of the sample, which indicates that the aerogel has excellent flame retardant property in the combustion process.
Example 2
Taking 1g of cellulose protoplasm, 0.015g of tetramethylpiperidine nitrogen oxide, 0.06g of sodium bromide and 100mL of deionized water in a beaker, mixing and stirring uniformly, adding 6mL of sodium hypochlorite solution with the mass fraction of 10%, and continuously stirring and reacting for 5 hours; during the reaction, the pH of the system was kept constant at 10.5 by dropwise addition of 0.5mol/L sodium hydroxide solution. Subsequently, the resulting mixture was mechanically treated with a household mixer at a rotation speed of 1000r/min, and after 30 minutes was washed with deionized water to obtain a nanocellulose suspension.
The resulting nanocellulose suspension was mixed with methyltrimethoxysilane hydrolysate obtained at pH 3, according to a 1: 0.25, stirring and mixing for 10 minutes in a household stirrer at the rotating speed of 1200r/min, and then slowly dropwise adding a 10% calcium chloride solution to obtain the composite nano cellulose hydrogel.
And (3) carrying out solution replacement on the obtained composite nano-cellulose hydrogel in an ethanol solution containing 10% by mass of p-toluenesulfonic acid, pouring the waste liquid every 8 hours, replacing the ethanol solution of the p-toluenesulfonic acid, and replacing for 24 hours to obtain the alcoholic gel containing the p-toluenesulfonic acid.
And (3) placing the alcogel on a directional freezing device, performing directional freezing for 3h by using liquid nitrogen, and then performing freeze drying for 48 hours in a freeze dryer to obtain the nano-cellulose composite aerogel material.
The thermal conductivity of the nano-cellulose composite aerogel obtained in example 2 is 0.035W/m.K, and the nano-cellulose composite aerogel has excellent heat insulation performance. As can be seen from fig. 4, the thermogravimetric residual amount of the nanocellulose composite aerogel obtained in example 2 is 54%, which is significantly increased compared to the nanocellulose composite aerogel obtained in example 1, mainly because the silicon content in the aerogel is increased due to the increase of the methyltrimethoxysilane content, thereby further reducing the proportion of combustible substances. In addition, according to the result of the limit oxygen index, the limit oxygen index value of the nano-cellulose composite aerogel obtained in example 2 is 46.6%, which is slightly higher than the value corresponding to example 1.
Example 3
Taking 1g of cellulose protoplasm, 0.015g of tetramethylpiperidine nitrogen oxide, 0.06g of sodium bromide and 100mL of deionized water in a beaker, mixing and stirring uniformly, adding 6mL of sodium hypochlorite solution with the mass fraction of 10%, and continuously stirring and reacting for 5 hours; during the reaction, the pH of the system was kept constant at 10.5 by dropwise addition of 0.5mol/L sodium hydroxide solution. Subsequently, the resulting mixture was mechanically treated with a household mixer at a rotation speed of 1000r/min, and after 30 minutes was washed with deionized water to obtain a nanocellulose suspension.
The resulting nanocellulose suspension was mixed with methyltrimethoxysilane hydrolysate obtained at pH 3, according to a 1: 0.5, stirring and mixing for 10 minutes in a household stirrer at the rotating speed of 1200r/min, and then slowly dropwise adding a 10% calcium chloride solution to obtain the composite nano cellulose hydrogel.
And (3) carrying out solution replacement on the obtained composite nano-cellulose hydrogel in an ethanol solution containing 10% by mass of p-toluenesulfonic acid, pouring the waste liquid every 8 hours, replacing the ethanol solution of the p-toluenesulfonic acid, and replacing for 24 hours to obtain the alcoholic gel containing the p-toluenesulfonic acid.
And (3) placing the alcogel on a directional freezing device, performing directional freezing for 3h by using liquid nitrogen, and then performing freeze drying for 48 hours in a freeze dryer to obtain the nano-cellulose composite aerogel material.
The thermal conductivity of the nano-cellulose composite aerogel obtained in example 3 is 0.037W/m.K, and the nano-cellulose composite aerogel has excellent heat insulation performance. As can be seen from fig. 4, the thermogravimetric residual amount of the nanocellulose aerogel obtained in example 3 was 60.4%, which is greatly improved compared with the values corresponding to examples 1-2. According to the result of the limited oxygen index test, the limited oxygen index value of the nano-cellulose aerogel obtained in example 3 is 51%, which is also obviously improved compared with the corresponding value in example 2. These results all show that the flame retardant property can be effectively improved by increasing the content of methyltrimethoxysilane.
Cone calorimetry tests (at 35 kw/m) were carried out on the aerogels obtained in examples 1 to 32The radiant power of (a), wherein the combustion process of example 3 is shown in fig. 6, the combustion process of the aerogel obtained in example 3 is significantly reduced compared to a pure cellulose aerogel. As can be seen from FIG. 5, the aerogel prepared in example 3 has good integrity of the remaining sample after cone calorimetry. As can be seen from FIG. 7 in which the ignition time was plotted from the cone calorimetry test, it was found that the ignition time was at 35kW m-2Under the heat flow density of the nano-cellulose aerogel, after p-toluenesulfonic acid and methyltrimethoxysilane are added, the ignition time of the nano-cellulose composite aerogel obtained in example 3 is 39s, and is obviously prolonged compared with that of a pure cellulose aerogel, so that the nano-cellulose composite aerogel has excellent flame retardant property.
Comparative example 1
Taking 1g of cellulose protoplasm, 0.015g of tetramethylpiperidine nitrogen oxide, 0.06g of sodium bromide and 100mL of deionized water in a beaker, mixing and stirring uniformly, adding 6mL of sodium hypochlorite solution with the mass fraction of 10%, and continuously stirring and reacting for 5 hours; during the reaction, the pH of the system was kept constant at 10.5 by dropwise addition of 0.5mol/L sodium hydroxide solution. Subsequently, the resulting mixture was mechanically treated with a household mixer at a rotation speed of 1000r/min, and after 30 minutes was washed with deionized water to obtain a nanocellulose suspension.
And pouring the obtained nano-cellulose suspension into a mold, and then slowly dropwise adding a 10% calcium chloride solution to obtain the nano-cellulose hydrogel. The hydrogel was placed in a freeze dryer to freeze at-35 ℃ for 12 hours, followed by freeze drying in the freeze dryer for 48 hours to obtain a pure cellulose aerogel material.
As can be seen from fig. 3, the microstructure of the pure cellulose aerogel prepared in comparative example 1 exhibited a disordered morphology, mainly due to the disordered growth of ice crystals inside the gel. As can be seen from the thermogravimetric curve of fig. 4, the amount of the pure cellulose aerogel residual carbon prepared in comparative example 1 is significantly reduced compared to that of examples 1, 2 and 3.
As can be seen from fig. 6 of the cone calorimetry experiment process, compared to the nano cellulose composite aerogel prepared in example 3, the combustion process of the pure cellulose aerogel prepared in comparative example 1 is very severe, and the flame height is obviously increased.
As can be seen from the ignition time chart of fig. 7, by increasing the content of methyltrimethoxysilane, the ignition time of the prepared nanocellulose composite aerogel is gradually and rapidly increased to 39s at most, and is greatly prolonged compared with the ignition time (2s) of the pure cellulose aerogel prepared in comparative example 1, which indicates that the ignition time of the aerogel can be effectively prolonged and the flame retardant property can be increased by increasing the content of methyltrimethoxysilane.
In addition, as can be seen from fig. 8, in the cone combustion calorimetry experiment process, the total smoke generated by the pure cellulose aerogel prepared in comparative example 1 is the largest, and reaches 0.13m2. The total smoke yield of examples 1, 2 and 3 was greatly reduced by adding methyltrimethoxysilane and p-toluenesulfonic acid. Wherein the total smoke amount of the embodiment 1 is 0.00165m2The total smoke amount of the pure cellulose aerogel prepared in the comparative example 1 is only 1.2%. The addition of methyltrimethoxysilane and p-toluenesulfonic acid was shown to be beneficial in reducing the smoke yield of the cellulose aerogel combustion process. The results show that the nano-cellulose composite aerogel prepared by the method has excellent flame retardant property.
Comparative example 2
Taking 1g of cellulose protoplasm, 0.015g of tetramethylpiperidine nitrogen oxide, 0.06g of sodium bromide and 100mL of deionized water in a beaker, mixing and stirring uniformly, adding 6mL of sodium hypochlorite solution with the mass fraction of 10%, and continuously stirring and reacting for 5 hours; during the reaction, the pH of the system was kept constant at 10.5 by dropwise addition of 0.5mol/L sodium hydroxide solution. Subsequently, the resulting mixture was mechanically treated with a household mixer at a rotation speed of 1000r/min, and after 30 minutes was washed with deionized water to obtain a nanocellulose suspension.
And stirring and mixing the obtained nano-cellulose suspension in a household stirrer at the rotating speed of 1200r/min for 10 minutes, and then slowly dropwise adding a 10% calcium chloride solution to obtain the nano-cellulose hydrogel.
And (3) carrying out solution replacement on the obtained nano-cellulose hydrogel in an ethanol solution containing 10% by mass of p-toluenesulfonic acid, pouring the waste liquid every 8 hours, replacing the ethanol solution of the p-toluenesulfonic acid, and replacing for 24 hours to obtain the alcoholic gel containing the p-toluenesulfonic acid.
And (3) placing the alcogel on a directional freezing device, performing directional freezing for 3h by using liquid nitrogen, and then performing freeze drying for 48 h in a freeze dryer to obtain the nano-cellulose aerogel material containing the p-toluenesulfonic acid.
According to the thermogravimetric curve of fig. 4, the carbon residue of the nano-cellulose aerogel material containing p-toluenesulfonic acid prepared in comparative example 2 is greatly increased to 31% compared with comparative example 1, but is obviously less than that of examples 2 and 3. Therefore, the method combines the carbonizing agents such as p-toluenesulfonic acid and the like with the in-situ introduced silicifying agent, so that the carbon residue of the cellulose is greatly increased, and the effect is obviously better.
From the above embodiments, in the embodiments of the present invention, the nanocellulose suspension and the hydrolysate of siloxane under acidic conditions are rapidly stirred and mixed, and then calcium chloride is added to obtain the mixture hydrogel; carrying out solution replacement on the obtained hydrogel in an ethanol solution containing a carbonizing agent to obtain an alcogel containing p-toluenesulfonic acid; and directionally freezing the alcogel on a directional freezing device to obtain the flame-retardant nano-cellulose composite aerogel with a directional structure. The nano-cellulose composite aerogel prepared by the method has excellent flame retardance, excellent heat-insulating property, mechanical property and the like, and can be used as a heat-insulating material.
The above description is only a preferred embodiment of the present invention, and it should be noted that various modifications to these embodiments can be implemented by those skilled in the art without departing from the technical principle of the present invention, and these modifications should be construed as the scope of the present invention.
Claims (10)
1. A preparation method of flame-retardant nano-cellulose composite aerogel with an oriented structure comprises the following steps:
s1, mixing the nano-cellulose suspension with siloxane hydrolysate, and crosslinking through water-soluble metal salt to obtain the composite nano-cellulose hydrogel;
s2, carrying out solution replacement on the composite nano-cellulose hydrogel in an alcoholic solution containing a carbonizing agent to obtain an alcoholic gel containing the carbonizing agent; the carbonizing agent is selected from one or more of p-toluenesulfonic acid, diphenyl phosphonic acid and trifluoromethanesulfonic acid;
s3, directionally freezing the alcogel containing the carbonizing agent to obtain the flame-retardant nano cellulose composite aerogel with a directional structure.
2. The preparation method according to claim 1, wherein the siloxane hydrolysate is a solution of siloxane hydrolyzed under acidic conditions, and the siloxane is one or more selected from methyltrimethoxysilane and methyltriethoxysilane.
3. The method of claim 1, wherein the nanocellulose suspension is prepared by the steps of: in an alkaline environment, mixing cellulose raw pulp with tetramethyl piperidine nitrogen oxide, bromide, hypochlorite and water for reaction, and then carrying out mechanical treatment to obtain the nano cellulose suspension.
4. The preparation method of claim 3, wherein when the nano-cellulose suspension is prepared, the cellulose raw pulp is derived from one or more of eucalyptus, poplar and straw; the bromide is selected from one or more of sodium bromide, potassium bromide and iodine bromide; the mass ratio of the cellulose raw pulp to the tetramethylpiperidine nitrogen oxide to the bromide to the water is 1: 0.01-0.02: 0.05-0.1: 50.
5. the preparation method according to any one of claims 1 to 4, wherein in the step S1, the mass ratio of the nano-cellulose suspension to the siloxane hydrolysis liquid is 1:0.1 to 1.
6. The preparation method according to claim 5, wherein the step S1 is carried out under stirring conditions, and the stirring speed is 1000-1200 r/min; and adding a calcium chloride solution for crosslinking to obtain the composite nano cellulose hydrogel.
7. The method according to any one of claims 1 to 4, wherein in the step S2, the alcohol solution containing the carbonizing agent is an ethanol solution containing 5 to 10 wt% of p-toluenesulfonic acid.
8. The method according to claim 7, wherein in step S2, the ethanol solution of p-toluenesulfonic acid is replaced at intervals of 6-10 hours, and the replacement time is not less than 24 hours.
9. The method according to any one of claims 1 to 4, wherein in step S3, liquid nitrogen is selected for freeze-drying during the directional freezing; the temperature of freeze drying is 20-30 ℃; the freeze drying time is 24-36 h; the vacuum pressure for freeze drying is lower than 20 Pa.
10. The flame-retardant nanocellulose composite aerogel obtained by the production method according to any one of claims 1 to 9, which exhibits a layered structure in a cross section and has disordered cellular pores in a longitudinal section.
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Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN113248775A (en) * | 2021-05-21 | 2021-08-13 | 南京安纳全诺新材料科技有限公司 | Bacterial cellulose-silicon dioxide P-COF aerogel and preparation method and application thereof |
| CN113501683A (en) * | 2021-07-13 | 2021-10-15 | 浙江理工大学 | Preparation method of boehmite-nano cellulose fiber-halloysite composite flame-retardant material |
| CN113637234A (en) * | 2021-07-28 | 2021-11-12 | 江苏理工学院 | Elastic cellulose aerogel and preparation method and application thereof |
Citations (11)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN106517144A (en) * | 2016-11-15 | 2017-03-22 | 中国科学技术大学 | Method for preparing carbon nanofiber aerogel from wood |
| CN107840988A (en) * | 2017-11-24 | 2018-03-27 | 中国科学技术大学 | The preparation method and heat preserving and insulating material of a kind of nano-cellulose aerogel |
| US20180229471A1 (en) * | 2017-01-12 | 2018-08-16 | Northeastern University | Fire-retardant nanocellulose aerogels, and methods of preparation and uses thereof |
| US20180237608A1 (en) * | 2017-01-11 | 2018-08-23 | The Regents Of The University Of Colorado, A Body Corporate | Cellulos-enabled orientationally ordered flexible gels |
| CN108579626A (en) * | 2018-04-26 | 2018-09-28 | 南京林业大学 | The preparation method of Cellulose nanocrystal body/graphene/polyvinyl alcohol aeroge |
| CN109158089A (en) * | 2018-11-07 | 2019-01-08 | 福州大学 | A kind of sulfhydryl modified cellulose aerogels of ultrasonic wave added and preparation method |
| CN109516763A (en) * | 2019-01-07 | 2019-03-26 | 东华大学 | A kind of cellulose fibre/SiO2Aerogel composite and its preparation and application |
| CN110172185A (en) * | 2019-05-08 | 2019-08-27 | 南京林业大学 | A kind of anisotropy nano-cellulose aerogel and preparation method thereof and device |
| CN110330944A (en) * | 2019-07-02 | 2019-10-15 | 同济大学 | Derivative composite phase change energy-storing conductive material of natural timber and preparation method thereof |
| WO2019241603A1 (en) * | 2018-06-13 | 2019-12-19 | The Regents Of The University Of Colorado, A Body Corporate | Bacterial cellulose gels, process for producing and methods of use |
| CN111440353A (en) * | 2020-04-26 | 2020-07-24 | 云南中烟工业有限责任公司 | Preparation method of heat-conducting hydrophobic flame-retardant nano-cellulose aerogel |
-
2020
- 2020-12-24 CN CN202011545594.6A patent/CN112662015B/en active Active
Patent Citations (11)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN106517144A (en) * | 2016-11-15 | 2017-03-22 | 中国科学技术大学 | Method for preparing carbon nanofiber aerogel from wood |
| US20180237608A1 (en) * | 2017-01-11 | 2018-08-23 | The Regents Of The University Of Colorado, A Body Corporate | Cellulos-enabled orientationally ordered flexible gels |
| US20180229471A1 (en) * | 2017-01-12 | 2018-08-16 | Northeastern University | Fire-retardant nanocellulose aerogels, and methods of preparation and uses thereof |
| CN107840988A (en) * | 2017-11-24 | 2018-03-27 | 中国科学技术大学 | The preparation method and heat preserving and insulating material of a kind of nano-cellulose aerogel |
| CN108579626A (en) * | 2018-04-26 | 2018-09-28 | 南京林业大学 | The preparation method of Cellulose nanocrystal body/graphene/polyvinyl alcohol aeroge |
| WO2019241603A1 (en) * | 2018-06-13 | 2019-12-19 | The Regents Of The University Of Colorado, A Body Corporate | Bacterial cellulose gels, process for producing and methods of use |
| CN109158089A (en) * | 2018-11-07 | 2019-01-08 | 福州大学 | A kind of sulfhydryl modified cellulose aerogels of ultrasonic wave added and preparation method |
| CN109516763A (en) * | 2019-01-07 | 2019-03-26 | 东华大学 | A kind of cellulose fibre/SiO2Aerogel composite and its preparation and application |
| CN110172185A (en) * | 2019-05-08 | 2019-08-27 | 南京林业大学 | A kind of anisotropy nano-cellulose aerogel and preparation method thereof and device |
| CN110330944A (en) * | 2019-07-02 | 2019-10-15 | 同济大学 | Derivative composite phase change energy-storing conductive material of natural timber and preparation method thereof |
| CN111440353A (en) * | 2020-04-26 | 2020-07-24 | 云南中烟工业有限责任公司 | Preparation method of heat-conducting hydrophobic flame-retardant nano-cellulose aerogel |
Non-Patent Citations (1)
| Title |
|---|
| YUAN CHEN: "Dual-Enhanced Hydrophobic and Mechanical Properties of Long-Range 3D Anisotropic Binary-Composite Nanocellulose Foams via Bidirectional Gradient Freezing", 《ACS SUSTAINABLE CHEMISTRY & ENGINEERING》 * |
Cited By (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN113248775A (en) * | 2021-05-21 | 2021-08-13 | 南京安纳全诺新材料科技有限公司 | Bacterial cellulose-silicon dioxide P-COF aerogel and preparation method and application thereof |
| CN113501683A (en) * | 2021-07-13 | 2021-10-15 | 浙江理工大学 | Preparation method of boehmite-nano cellulose fiber-halloysite composite flame-retardant material |
| CN113501683B (en) * | 2021-07-13 | 2022-06-21 | 浙江理工大学 | Preparation method of boehmite-nano cellulose fiber-halloysite composite flame-retardant material |
| CN113637234A (en) * | 2021-07-28 | 2021-11-12 | 江苏理工学院 | Elastic cellulose aerogel and preparation method and application thereof |
| CN113637234B (en) * | 2021-07-28 | 2023-03-17 | 江苏理工学院 | Elastic cellulose aerogel and preparation method and application thereof |
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