CN111320780B - Polyimide/polyethylene oxide composite aerogel and preparation method thereof - Google Patents

Abstract

Discloses a polyimide/polyethylene oxide composite aerogel and a preparation method thereof, wherein the method comprises the following steps: (1) dissolving polyethylene oxide in LNMP to form a solution A; (2) dissolving ODA in LNMP, stirring, adding BPDA after the ODA is completely dissolved, and stirring until the reactant becomes transparent to form a solution B; (3) dissolving a cross-linking agent TAB in 12mL of NMP to form a solution C; (4) pouring the solution C into the solution B, and stirring at room temperature to form a transparent solution BC; (5) mixing and stirring the solution BC and the solution A to obtain a mixed solution, adding acetic anhydride and pyridine, stirring, and pouring into a mold; (6) gelling and aging in a sealed environment, and then soaking in an acetone solution; (7) by supercritical CO₂And after drying by the drying method, drying the sample in a vacuum drying oven to remove the residual solvent, wherein the content numerical value of each component is used for representing the proportional relation among the contents of each component, and the numerical values of the contents of each component and the process parameters represent the range of 15 percent above and below the numerical value.

Description

Polyimide/polyethylene oxide composite aerogel and preparation method thereof

Technical Field

The invention relates to the technical field of organic aerogel, in particular to polyimide/polyethylene oxide composite aerogel and a preparation method thereof.

Background

The aerogel is a solid material with a nano porous structure, has the characteristics of high porosity, high specific surface area, low density, low heat conductivity coefficient and the like, and has great application potential in the aspects of heat insulation, adsorption, catalyst carriers, energy storage, water purification, cosmic dust collection, sensors, noise elimination and the like. The aerogel is a solid substance with the minimum density in the world, has very high porosity which can reach 80-99.8%, and has lower density which is 0.003-0.5 g/cm³In between. Nano-meterThe high porosity of the holes ensures that the aerogel has extremely low heat conductivity coefficient and better heat insulation performance. The lower density also makes it the first choice for light heat insulating materials such as satellites and submarines. Aerogels are mainly classified into inorganic aerogels and organic aerogels. The silicon dioxide aerogel is taken as a representative of inorganic aerogel, the research and the industrialization work of the silicon dioxide aerogel are carried out comprehensively all over the world, but the silicon dioxide aerogel also has the defects of poor mechanical property and frangibility, and is not suitable to be used as a material independently, and is generally made into a composite aerogel material with other inorganic or organic materials for application. The organic aerogel mainly comprises aerogel made of materials such as Polyimide (PI), polyurethane, phenolic aldehyde and the like, and has the advantages of excellent comprehensive performance and easiness in processing and application. Among organic aerogels, polyimide aerogel attracts people's attention due to its excellent mechanical properties, good thermal stability, and low thermal conductivity and dielectric constant. The polyimide is the material with the most excellent comprehensive performance in high polymer materials, has higher mechanical property and thermal property, has more synthesis and forming methods, and is easy to obtain different types of polyimide materials. In recent years, scientific research institutions at home and abroad carry out systematic research on polyimide aerogel, but the subject and knowledge aspects related to the preparation of the polyimide aerogel are relatively complex, the technical threshold is relatively high, only a few institutions all over the world have the technology for preparing the polyimide aerogel, the practical application of the polyimide aerogel is more rare, and the industrialization process of the polyimide aerogel is far away.

At present, for the synthesis of polyimide aerogel, a dupont process method is mainly adopted: firstly, diamine and dianhydride react at room temperature to prepare polyamic acid solution, and then the polyamic acid solution is dehydrated by a chemical method (acetic anhydride is used as a dehydrating agent and pyridine is used as a catalyst) or at high temperature to complete amidation reaction to form polyimide gel. Because the macromolecular chain of the polyimide has a highly conjugated aromatic structure, the polyimide is easy to form a closely-packed nanofiber structure through T-T packing and molecular chain entanglement in the gelling process, so that the polyimide aerogel is endowed with unique thermal oxidation stability, high mechanical strength and solvent resistance. Thus, polyimide aerogels have thermo-oxidative stability, unique electrical properties, high radiation and solvent resistance, and excellent mechanical strength. Compared with dehydration amidation at high temperature, the chemical method has relatively mild conditions and higher efficiency.

Epoxy resins are widely used in many reinforcing materials due to their good mechanical properties, processing properties, compatibility with most fibers, chemical resistance, abrasion resistance and low cost. The polyethylene oxide has good solubility and excellent wire-drawing gel concentration at room temperature, has good plasticity, and is nontoxic and harmless. However, there is no solution in the prior art to compound polyethylene oxide with polyimide to produce aerogel to improve its performance.

Disclosure of Invention

In one aspect of the present invention, there is provided a method for preparing a polyimide/polyethylene oxide composite aerogel, comprising the steps of:

(1) dissolving polyethylene oxide (PEG-20000) in 1-methyl-2-pyrrolidone (NMP) to form a solution A;

(2) dissolving 4-aminodiphenyl ether (ODA) in 1-methyl-2-pyrrolidone, stirring, adding 3,3',4,4' -biphenyl tetracarboxylic dianhydride (BPDA) after the mixture is completely dissolved, and stirring until reactants become transparent to form a solution B;

(3) dissolving a cross-linking agent 1,3, 5-tri (4-aminophenoxy) benzene (TAB) in 12mL of 1-methyl-2-pyrrolidone to form a solution C;

(4) pouring the solution C into the solution B, and stirring at room temperature to form a transparent solution BC;

(5) mixing and stirring the solution BC and the solution A to form a mixed solution, adding acetic anhydride and pyridine, stirring and pouring into a mold;

(6) gelling and aging in a sealed environment, and then soaking in an acetone solution; and

(7) by supercritical CO₂Drying method after drying, the sample was placed in a drying oven to be dried to remove the residual solvent.

In another aspect of the present invention, there is provided a polyimide/polyethylene oxide composite aerogel prepared using a method of preparing a polyimide/polyethylene oxide composite aerogel according to any one of the embodiments of the present invention.

According to the embodiment of the invention, 4-aminodiphenyl ether and 3,3',4,4' -biphenyl tetracarboxylic dianhydride are used as monomers, 1,3, 5-tri (4-aminophenoxy) benzene is used as a cross-linking agent to prepare polyimide aerogel, the polyimide and polyethylene oxide are mixed to prepare composite aerogel, and after the ethylene oxide is added, the porosity and the average pore diameter of the aerogel can be improved, and the toughness is enhanced.

Drawings

Fig. 1 illustrates a method for preparing a polyimide/polyethylene oxide composite aerogel according to an embodiment of the present invention.

FIG. 2 shows scanning electron micrographs of a pure polyimide aerogel and a polyimide/polyethylene oxide (16: 4) composite aerogel produced according to the method of an embodiment of the present invention.

Detailed Description

Embodiments of the present invention are described in detail below with reference to the accompanying drawings. In the following description, numerous specific details are set forth in order to provide a more thorough understanding of the present invention to those of ordinary skill in the art. It will be apparent, however, to one skilled in the art that the present invention may be practiced without some of these specific details. Furthermore, it should be understood that the invention is not limited to the specific embodiments described. Rather, any combination of the following features and elements, whether related to different embodiments or not, is contemplated to implement the invention. Thus, the following aspects, features, embodiments and advantages are merely illustrative and should not be considered elements or limitations of the claims except where explicitly recited in a claim. The meaning of each term referred to in this specification is generally a meaning commonly understood in the art or a meaning normally understood by those skilled in the art after reading this specification. The terms "comprising" and "including" in this specification are open-ended, i.e., may include additional elements not already mentioned in addition to the elements already mentioned. The specific values of the contents of the components described in the present specification are only used to indicate a proportional relationship between the contents of the components, and are not used to limit the contents of the components to any absolute values. Specific values for the amounts of ingredients and specific values for the process parameters described in this specification are intended to be inclusive, e.g., 15% inclusive, and not intended to be limiting to a precise value.

Referring now to fig. 1, a method of preparing a polyimide/polyethylene oxide composite aerogel according to an embodiment of the present invention is shown. As shown in fig. 1, the method comprises the steps of:

(1) dissolving polyethylene oxide in 1-methyl-2-pyrrolidone to form a solution A;

(2) dissolving 4-aminodiphenyl ether in 1-methyl-2-pyrrolidone, stirring, adding 3,3',4,4' -biphenyl tetracarboxylic dianhydride after the 4-aminodiphenyl ether is completely dissolved, and stirring until reactants become transparent to form a solution B;

(3) dissolving a cross-linking agent 1,3, 5-tri (4-aminophenoxy) benzene in 1-methyl-2-pyrrolidone to form a solution C;

(4) pouring the solution C into the solution B, and stirring at room temperature to form a transparent solution BC;

(5) mixing and stirring the solution BC and the solution A to form a mixed solution, adding acetic anhydride and pyridine, stirring and pouring into a mold;

(6) gelling and aging in a sealed environment, and soaking in an acetone solution; and

(7) by supercritical CO₂Drying method after drying, the sample was placed in a vacuum oven for drying to remove residual solvent.

In some embodiments, in step (1), 4g of polyethylene oxide is dissolved in 80mL of 1-methyl-2-pyrrolidone to form solution a, wherein the numerical value of each ingredient content is used to represent the proportional relationship between each ingredient content, and the numerical values of each ingredient content and process parameters represent the range of 15% above and below the numerical value.

In some examples, in said step (2), 1.58g of 4-aminodiphenyl ether is dissolved in 66mL of 1-methyl-2-pyrrolidone and stirred, after it is completely dissolved, 2.395g of 3,3',4,4' -biphenyltetracarboxylic dianhydride is added and stirred until the reactant becomes transparent to form a solution B.

In some embodiments, in step (3), 0.07g of the crosslinker 1,3, 5-tris (4-aminophenoxy) benzene is dissolved in 12mL of 1-methyl-2-pyrrolidone to form solution C.

In some embodiments, in step (4), after pouring solution C into solution B, stirring is performed at room temperature for about 20 minutes.

In some embodiments, in step (5), solution BC and solution A are mixed in a volume ratio of 20:0, and 1.55mL of acetic anhydride and 1.30mL of pyridine are added.

In other embodiments, in step (5), solution BC and solution A are mixed in a volume ratio of 18:2, and 1.40mL of acetic anhydride and 1.20mL of pyridine are added.

In still other embodiments, in step (5), solution BC and solution A are mixed in a volume ratio of 16:4, and 1.25mL of acetic anhydride and 1.05mL of pyridine are added.

In still other embodiments, in step (5), solution BC and solution A are mixed in a volume ratio of 15:5, and 1.15mL of acetic anhydride and 1.00mL of pyridine are added.

In some embodiments, in the step (5), the solution BC and the solution a are mixed and stirred for about 20 minutes to form a mixed solution, and after adding acetic anhydride and pyridine, the mixed solution is stirred for about 1 minute and poured into a mold.

In some embodiments, in step (6), after gelling and aging in a sealed environment for about 24 hours, soaking with an acetone solution.

In some embodiments, in the step (6), the soaking with an acetone solution comprises:

soaking in acetone solution containing 75% of 1-methyl-2-pyrrolidone, soaking in acetone solution containing 50% of 1-methyl-2-pyrrolidone, soaking in acetone solution containing 25% of 1-methyl-2-pyrrolidone, and soaking in pure acetone solution.

In some further embodiments, the soaking with an acetone solution comprises:

the method comprises the steps of soaking for about 24 hours by using an acetone solution containing 75% of NMP, soaking for about 24 hours by using an acetone solution containing 50% of NMP, soaking for about 24 hours by using an acetone solution containing 25% of NMP, and soaking for about 24 hours by using a pure acetone solution.

In some embodiments, in step (7), supercritical CO is used₂Drying method after drying at about 50 ℃ under 10MPa for about 18 hours, the sample was dried in a vacuum oven at about 70 ℃ for about 18 hours to remove the residual solvent.

The method for preparing a polyimide/polyethylene oxide composite aerogel according to the embodiments of the present invention is described above with reference to the accompanying drawings, and it should be noted that the above description is only an example and not a limitation of the present invention. In other embodiments of the invention, the method may include more, fewer, or different process steps, and the ingredients, proportions, and process conditions and parameters in the various process steps may differ from those described and illustrated.

In another aspect of the present invention, there is also provided a polyimide/polyethylene oxide composite aerogel prepared using a method of preparing a polyimide/polyethylene oxide composite aerogel according to any one of the embodiments of the present invention.

One specific embodiment of the present invention is described below:

1 preparation method

1.1 Main raw materials

4-aminodiphenyl ether (ODA), 3,3',4,4' -biphenyltetracarboxylic dianhydride (BPDA), polyethylene oxide (PEG-20000), 1,3, 5-tris (4-aminophenoxy) benzene (TAB), 1-methyl-2-pyrrolidone (NMP), pyridine, acetic anhydride, acetone.

1.2 sample preparation

4g PEG-20000 is dissolved in 80m LNMP to form solution A; dissolving 1.58g of ODA in 66mL of NMP solvent, stirring, adding 2.395g of BPDA after the ODA is completely dissolved, and stirring until the reactant becomes transparent to form a solution B; 0.07g of the crosslinking agent 1,3, 5-tris (4-aminophenoxy) benzene (TAB) was dissolved in 12mL of NMP to form solution C. Solution C was then poured into solution B and stirred at room temperature for 20 minutes to form a clear solution BC. Mixing the solution BC and the solution A according to the volume ratio of 20:0,18:2,16:4 and 15:5 and stirring for 15 minutes to form mixed solutions, wherein the numbers are 1, 1 and,2.3 and 4. To the four solutions were added 1.55 acetic anhydride and 1.30 pyridine, 1.40 acetic anhydride and 1.20 pyridine, 1.25 acetic anhydride and 1.05 pyridine, 1.15 acetic anhydride and 1.00mL pyridine, respectively, in that order, stirred for 1 minute and poured into a mold. After the gel is aged in a sealed environment for 24 hours, the gel is soaked in an acetone solution containing 75% of NMP for 24 hours, then soaked in an acetone solution containing 50% of NMP for 24 hours, then soaked in an acetone solution containing 25% of NMP for 24 hours, and finally soaked in a pure acetone solution for 24 hours. By supercritical CO₂Drying method at 50 deg.C under 10MPa for 18 hr, and drying the sample in 70 deg.C vacuum oven for 24 hr to remove residual solvent.

2 results and analysis

2.1 specific surface area and pore size analysis

TABLE 1 comparison of pore structures of polyimide/polyethylene oxide composite aerogels

The specific surface area is reduced due to the addition of polyethylene oxide, and when the ratio of the polyimide to the polyethylene oxide is 18:2, the specific surface area is reduced to 436m²(ii)/g; when the ratio was increased to 16:4, the specific surface area dropped to 354.1m²In terms of/g, further increases in the polyethylene oxide content have little effect on the specific surface area. The average pore diameter of the composite aerogel material is between 17 and 23 nm. The porosity of the pure polyimide aerogel is the lowest, and when polyethylene oxide is added, the porosity is obviously increased. This is because a part of the ethylene oxide molecular chains is fixed in the gel in the form of free-running chains after the addition of polyethylene oxide. When the wet gel is soaked in a solvent, this portion of the molecules is washed out by dissolution due to excellent solubility.

2.2 morphological analysis

FIG. 2 shows scanning electron micrographs of pure polyimide aerogel and a polyimide/polyethylene oxide (16: 4) composite aerogel. As can be seen from fig. 2, the composite aerogel is a fibrous structure like the pure polyimide aerogel. Compared with pure polyimide aerogel, the polyimide/polyethylene oxide composite aerogel fiber structure is slightly thin. The reason is that after the flexible molecular chain of polyethylene oxide is added, the entanglement and induction of the flexible chain affect the accumulation of polyimide molecules, so that a composite fiber structure of the two is formed.

2.3 Strain Curve and modulus

After being subjected to pressure, the aerogel is strained in three phases: the first stage, elastic deformation stage, the deformation of aerogel is elastic deformation, and the macroscopic structure and the microscopic structure of aerogel can be recovered after releasing external force; in the second stage, in the bending deformation stage, the stress borne by the aerogel exceeds the bearing range, the internal structure is damaged, and the framework structure collapses; the third stage, the inside compression stage, along with the increase of the aerogel stress that receives and inner structure's destruction, the inside hole of aerogel disappears gradually, and the aerogel becomes more closely knit, and the aerogel after the compression becomes compact block.

In the first stage of straining from the aerogel, the pure polyimide aerogel has a relatively high young's modulus of 8.21 MPa. When a small amount of polyethylene oxide is added into the aerogel, the Young modulus of the aerogel is reduced to 6.74 MPa, and the mechanical strength is not obviously changed when the content of the polyethylene oxide is continuously increased. In the second stage of strain, after a small amount of polyethylene oxide is added, the plastic deformation range of the aerogel is enlarged, and the toughness is improved.

Therefore, the composite aerogel prepared according to the embodiment of the invention can improve the porosity and average pore diameter of the aerogel along with the addition of polyethylene oxide, has strong toughness, good elasticity and strength, and can be applied under the working condition of harsh mechanical conditions.

Although the present invention has been disclosed above by way of examples, the present invention is not limited thereto. Various changes and modifications within the spirit and scope of the invention may be effected by those skilled in the art without departing from the spirit and scope of the invention, which is to be limited only by the language of the claims and the equivalents thereof.

Claims (3)

1. A preparation method of polyimide/polyethylene oxide composite aerogel comprises the following steps:

(1) dissolving 4g of polyethylene oxide in 80mL of 1-methyl-2-pyrrolidone to form a solution A;

(2) dissolving 1.58g of 4-aminodiphenyl ether in 66mL of 1-methyl-2-pyrrolidone, stirring, adding 2.395g of 3,3',4,4' -biphenyl tetracarboxylic dianhydride after the 4-aminodiphenyl ether is completely dissolved, and stirring until a reactant becomes transparent to form a solution B;

(3) 0.07g of a crosslinking agent 1,3, 5-tris (4-aminophenoxy) benzene was dissolved in 12mL of 1-methyl-2-pyrrolidone to form a solution C;

(4) pouring the solution C into the solution B, and stirring at room temperature to form a transparent solution BC;

(5) mixing and stirring the solution BC and the solution A according to the volume ratio of 18:2,16:4 or 15:5 to form a mixed solution, respectively adding 1.40mL, 1.25mL or 1.15mL of acetic anhydride and 1.20mL, 1.05mL or 1.00mL of pyridine, stirring and pouring into a mold;

(6) gelling and aging in a sealed environment, and soaking in an acetone solution; and

(7) by supercritical CO₂After drying by the drying method, putting the sample in a vacuum drying oven for drying so as to remove residual solvent;

wherein, the numerical value of each component content is used for expressing the proportional relation among the component contents, and the numerical value of each component content and the process parameter expresses the range of 15 percent above and below the numerical value.

2. The method of claim 1, wherein, in the step (6), the soaking with the acetone solution comprises:

soaking in acetone solution containing 75% of 1-methyl-2-pyrrolidone, soaking in acetone solution containing 50% of 1-methyl-2-pyrrolidone, soaking in acetone solution containing 25% of 1-methyl-2-pyrrolidone, and soaking in pure acetone solution.

3. A polyimide/polyethylene oxide composite aerogel prepared using a preparation method of a polyimide/polyethylene oxide composite aerogel according to claim 1 or 2.

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